It really doesn't matter who you pick, it's how you train them. All three are powerful at their last stages, so keep them in your party and level them up.
battlefrontiertrainer, you might want to delete one of those posts. And I say the same as all, you should pick the one you like the most and get the other two on later in the game.
Over and out,;198;
I chose Bayleef because you can't get any good grass types for some time and if I am not mistaken there are only 4 grass types: Bayleef, Skiploom, Sunflora and Tropius.
I also would recommend Bayleef because it makes a good tank, and is one of the few good grass types. Also, you can use Entei and Suicune to cover fire and water.
It doesn't really matter what you pick. But I suggest Croconaw. ^^ I read in my handbook that there were some rock type Pokemon at the beginning, so it might come in handy. I think Bayleef is best second, because of its grass moves. But, remember that you can pick any kind of type that you like most. ^^
IMHO, Bayleef is the best choice since along with Espeon and Umbreon and the 3 legendary dogs/cats/whatever you want to call them, there aren't any type conflicts.
Bayleed because Meganium is an amazing pokemon, but then so are Feraligatr and Typhlosion, I personally would pick Bayleef, but from an unbiased opinion it doesn't really matter, whichever one you want.
I found Meganium to be most useful, but that's just me.
Feraligatr was okay. Typhlosion didn't help at all.
I'd go with Meganium though, since Entei and Suicune are just as good as Feraligatr and Typhlosion in Colosseum, and it's hard to find a good Grass type.