I pick Jotho, because I have very found memories of the second region. Cyndaquil (and with it Typhlosion) is one of my favourite (Fire) Pokemon, if Typhlosion isn't still my fav Pokémon. :3
Chicorita is cute, but I like Bayleef and Meganium more. :3 Totodile was awesome in the Anime, Croconaw and Feraligatr (the latter more than the first) are cool. XD
Then it's gotta be a tie between Hoenn and Kanto.
I like Charmander (Charmeleon and Charizard) a lot. Charizard is, along with Blaziken and Typhlosion, a very cool Pokemon (odd, cool for Fire Pokemon). And I like Dragons. :3 I also think that Charmander was one of my first Pokémon cards (of the first series 8D I had it in English and Dutch (back when cards were still translated). :0)
Squirtle is one of those Pokémon I'll never grow bored of. I was a squirtle in Mystery Dungeon, and I refused to evolve into a Blastoise. I like Wartortle way to much. x3 (I guess it's one of the Pokémon I drew in my beginning anime phase)
As for Bulbasaur, I never cared much about that Pokémon, though I don't hate it. 8O
Now Hoenn, of course I like Hoenn... If I didn't, then why would my previous username have been Mudkipblader? And I couldn't care less about "I herd u like Mudkipz", I liked Mudkip before I heard of it.. >: Swampert's ground type, made it a very good Pokémon, with it's only major weakness being grass.
Treecko not so much, but Grovyle was awesome. 8D Leaf Blade sounds like such a cool attack. And Sceptile was nice as well, though I prefer Grovyle.
Torchic is probably one of the cutest starters of them all... And Blaziken, with Combusken, is an awesome Pokemon, and one of my Battle Frontier trio.
As for Sinnoh, no thank you. I didn't like any of the starters, nor their evolutions.
Piplup and Turtwig were those that I "prefered"...