The gym rosters are staying the same now? Blegh. That sucks. I'm seriously disappointed now. Metapod and Kakuna are really pathetic for the second gym. I'd have loved to have seen them evolve, or maybe Spinarak or Ledyba come in. Sure, they want to make it easier for the Chikorita line, but it's not like they've held back that much in other games. If you picked Charmander, Misty still has a Starmie, one of the best Pokemon in the game. And if you face Gardenia with a Piplup, then too bad, 'cos she has a Roserade, a Pokemon also used by this region's Champion.
By the second gym, you've caught a lot of new Pokemon anyway, the aim is not just to go through with your starter. Here's a list of Pokemon catchable before the second gym, all with super-effective STAB attacks against Bug, Poison and/or Flying (the types involved with Bugsy's roster).
Geodude
Onix
Spearow
Pidgey
Hoothoot
Slowpoke
Mareep
Zubat
Growlithe (Crystal)
I'm not even including the Goldeen with Peck, or the Sandshrew and Phanphy with Rollout.
EDIT: And now Whitney's been nerfed. Rubbish. The games always needed a challenge, that Miltank was one of the best things about GSC's gyms.