>>25261660Black and White or B2W2, by far. Anybody who says differently has no idea what they're talking about.
My vote goes for BW, though. Venipede and Sewaddle are available as early on as before the second gym, you can get the Larvesta egg before the E4, and you can catch Karrablast, Shelmet, Dwebble, and others along the way.
ORAS/RSE might not be bad, as well. All the bugs in Gen IV are way too weak at the game's beginning, I'd reckon.