Oh, favorite. Not sure I can pick just one, but a couple tops are Treecko and Snivy. I'm okay with the other grass starters, except for Chikorita. Only good one from Gen 2 was Cyndaquil. I like the Gen 3, okay with Gen 1, not a big fan of Gen 4, and Gen 5 is everywhere (Snivy=yes; Oshowatt=it's fine; Tepig=no)
Bottoms: Chikorita, Totodile, Tepig. Not much to say, just a lack of appeal here for me.