Best of TYPE according to Versus Books. Mousing over the Pokemon will reveal their average stats at level 100.

Best of type: FIRE Has Entei stolen Arcanine's crown?  Surprisingly, their stats are nearly identical.  Arcanine learns its power moves earlier, but you'll need to use a TM to teach it Fireblast, which Entei learns naturally.  We'll have to call this one a tie, but it's a moot point if you have space for an extra Flyer in your party, since a Ho-0h raised from level 40 smokes them both.  (Since Flyers do have serious weaknesses, it's best not to use more than one or two at once.)

#059 Arcanine

#244 Entei

Best of type: Fighting Hitmonlee still seems to be the game's best fighter.  In fact, its new Special Defense boost makes it even stronger than before, and Fighters are likely to be more useful if Dark and Steel-types catch on.  Hitmontop is cute and has nice stats, but its shortage of attack moves is too severe of an obstacle to overcome.

#106 Hitmonlee

#237 Hitmontop

Best of type: Electric Jolteon topped this category last time, but its stats have been brought down a few notches in G/S.  Raikou, the only viable challenger, is a bit slower than Jolteon (though still faster than most Pokemon), but has a higher Special Attack and Defense.  Its skill selection is limited, but it does get Spark and Thunder.  If you're willing to invest the time necessary to get it to level 70 +, it probably is a better overall pokemon.  Still, Jolteon's Pin Missile is a necessity if your team has trouble dealing with Psychics.

#243 Raikou

#135 Jolteon

Best of type: Bug The only reason most people play Bug Pokemon is for their strength against Psychics.  Now that the Dark has taken on that role, Bug-type isn't too usefull... But it's that same strength against Dark that will make it worth looking at if Dark becomes popular.  Heracross is the sole Pokemon that can learn Bug's power move, Megahorn, which is tempting... But its half-Fighting nature negates its strength against Psychics.  So it's half-Steel Scizor that wins this one.  Its loss of Scyther's Speed is unfortunate, but it makes up for it with good Defense and a variety of decent moves (make sure to teach it Fury Cutter.

#212 Scizor

#214 Heracross

Best of type: Grass Suddenly, there are a ton of great pure-Grass Pokemon to choose from.  We picked the so-so Tangela as the champ for R/B/Y, because Venusaur's half-Poison nature made it too weak to Psychics.  Meganium, thankfully, is pure Grass, and has strong stats on Defense.  It doesn't have many stand-out moves (Synthesis and Body Slam are solid), but if you use TM 19 to teach it Giga Drain, it can be a good fighter.  Bellosssom is a close second, with inferior stats but strong attack moves like Petal Dance.

#154 Meganium

#182 Bellossom

Best of type: Poison With vulnerability to the game's strongest type (Psychic) and only one good high-level attack (Toxic), Poison was one of the worst types in the previous version.  The news in G/S is mixed:  With both Sludge Bomb and Toxic as TM's, Poison finally has a decent set of high level moves.  But with no new Poison Pokemon of note, those TM's are best used on half poison Gengar or Defensive powerhouse Shuckle.  Weezing and Muk are okay, but the weaknesses of their type are still too severe.

#213 Shuckle

#094 Gengar

Best of type: ICE We gave this one to Cloyster last time, but its lower Special Defense in G/S has caused most of us to replace it in our teams with trusty Lapras.  Lapras has solid stats, a good mix of Ice and Water attacks (it can easily fill both slots in your party), and better Defense against Special Attacks.  Cloyster and Articuno are strong seconds, but none of the new Ice-types (Delibird, Sneasel, Swinub and Piloswine) impressed us much.

#131 Lapras

#091 Cloyster

Best of type: Water There are a ton of new Water Pokemon, but only Suicune and Feraligatr have a strong shot at Blastoise's title.  Suicune beats Feraligatr at both stats and moves, so it's between that new legend and good 'ol Blastoise.  They're very similar Pokemon, actually, but Suicune's superior Defense will triumph in the end... But only if you're willing to raise your Suicune high enough to learn Hydropump.

#245 Suicune

#009 Blastoise

Best of type: Flying The best Flyers tend to be the ones with a sub-type that rounds out Flying's weaknesses.  Last time we picked Aerodactyl, whose secondary Rock-type and phenomenal Speed gave it a fighting chance against even Electric Pokemon.  Silver now has half-Steel Skarmony, with a type mix that is good against almost everything.  They're both great Pokemon, but the champ is of course, Lugia.  Flying and Psychic don't have greast synergy, but Lugia has the game's best Flying technique, Aeroblast, and the best stats in the game.  It's hard to argue with that.

#249 Lugia

#227 Skarmony

Best of type: Ghost Gengar finally has some competition, in the form of the series' first pure Ghost, Misdreavus.  Pure-Ghost is a great type, with a good set of strengths and immunities that Gengar can't take full advantage of, being part Poison.  But Gengar is by far the better Pokemon, with great stats (it just missed the top 20) and good moves.  Misdreavus' stats are disappointing, but it does have a lot of fun moves, and is certainly worthy of an honorable mention.

#094 Gengar

#200 Misdreavus

Best of type: Psychic Lugia's a contender here too, but Mewtwo's focus on a single type and its through-the-roof Special Attack makes it the champ.  Yeah, Psychics can't hurt Dark-types and aren't great against Steel, but how many of those do you see?  Mewtwo still reigns supreme.  Of course, you can't get Mewtwo in G/S, so newcomers will want to get their hands on Espeon, a strong # 2 with much lower stats, but a few neat tricks.  If you let it learn Bite as Eevee, it'll be able to take down your opponent's Psychics with relative ease.  Even Mewtwo!

#150 Mewtwo

#196 Espion

Best of type: Dragon Thanks to Kingdra, Dragonite no longer has to suffer the shame of winning this category merely by default.  Dragonite has better stats, but it's actually a tight contest.  Kingdra's combination of Water and Dragon types erases all of its weaknesses, making it a very reliable Pokemon.  Of course, Dragonite's pretty tough too:  Its only real weakness is Ice.  Dragonite has a slightly better selection of moves, with both Hyper Beam and the new Dragon-type Outrage.  But it's a tough call, and both are great Pokemon.

#230 Kingdra

#149 Dragonite

Best of type: Ground Dugtrio won this crown by default last time, but now it has some serious competition from Silver-exclusive Donphan.  Donphan is weak to Special attacks, but has a very high normal Attack (which is what powers Ground attacks) and strong Defense.  It lacks Dugtrio's excellent Speed, but has most of the type's good moves, and can dish out serious damage with Earthquake.  Now that Dig isn't obscenely powerful anymore, Donphan is the Ground-type to best.

#232 Donphan

#051 Dugtrio

Best of type: Rock Rock was one of the weaker types in R/B/Y, but a bunch of strong new G/S Pokemon have changed all that.  Magcargo and Sudowoodo are playable, and Shuckle, despite its gimmicky nature, is surprisingly good.  Of course, none of those stand a chance against the mighty Tyranitar... I expect to see it almost as often as Mewtwo and Lugia in versus play.  And being half-Dark, that isn't good news for either of those champion Pokemon.

#248 Tyranitar

#213 Shuckle

Best of type: Steel Steel is a pretty nice type to dabble in, since it grants all sorts of resistances and very few weaknesses.  Since most competitive players rely on type-matching, using Steel can throw a monkey wrench into their plans.  Steelix may be slower than continental drift, but it's weak only to Fighting and Ground, both of which are fairly rare.  This can make Steelix a frustrating surprise for opponents who think they're ready for anything.  Skarmory, Forretress and Scizor are all playable as well.

#208 Steelix

#205 Forretress

Best of type: Dark Dark is a little too specialized to deserve its own slot in a well-rounded team (sorry Umbreon).  Instead, I like to use half Darks like Tyranitar and Houndoom, Houndoom mixes attacks from Fire-type (another type that doesn't always need its own slot) with the best Dark has to offer.  This mix gives Houndoom a lot of weaknesses to popular types, but let's face it, this guy wasn't built to stick around for a long time.  With the most powerful attacks of two types at its disposal, it is a great strike fighter that can do a lot of damage in a small amount of time.

#229 Houndoom

#248 Tyranitar

Best of type: Normal Normal is the largest type in the game, but is home to surprisingly few great Pokemon.  There are two solid new Normals in G/S: Ursaring and Porygon 2.  There isn't much nuance to Ursaring: It's just big and strong, with lots of strong Normal attacks.  This is the role Tauros played in R/B/Y, and it's hard to say which is better.  Porygon2 is different.  It has good stats, including the highest Special Attack of any normal Pokemon.  It uses this for powerful attacks like Psybeam and Zap Cannon, and with the ability to learn several TM's, Porygon 2 can be a versatile battler capable of using different attacks of different types effectively.  Finally we have to give a nod to Snorlax, a strong Pokemon who has a ton of cool new moves. Rest and Snore make a nice combo, and Hyper Beam provides the solid beating that this defensive Pokemon needs to finish the job.

#217 Ursaring

#128 Tauros

#233 Porygon 2

#143 Snorlax

This information is from the Collector's Edition Pokemon G/S Version Official Perfect Guide & Exclusive 90-Page Pokedex by Versus Books.  The web address on the inside cover is:  www.versusbooks.com  Apparently they haven't had a chance to put much up on the web yet.  You can get this fabulous guide at  Amazon.  I highly recommend that you purchase your own copy for easy reference of lots of great information.