Now that I think about it, thats a hard question. No gen had all starters I like. Gen 1 had Blastoise, Gen 2 had Feraligatr, Gen 3 had Swampert and Sceptile (I don't dislike either, they are just both meh), Gen 4 had Infernape and Torterra, and Gen 5 had Emboar.
I'm gonna go with Gen 3 here. for not having any starters I actually dislike.
Not changing this sig until we get a new main series Tales game released on a Nintendo console in the US