Well, since a lot of people are posting their favourite starters from each gen...
Gen I: Charmander, hands down. The other two are OK. Venusaur is meh (I like it but it's nothing special for me) and Blastoise is quite cool, but I love the entire Charmander line really - Charmander is cute as heck, Charmeleon is cool, and Charizard is just a beast. Yet ironically, the only one of the Kanto starters I've ended up really using so far has been Venusaur. :L
Gen II: I quite like these three. Chikorita is cute, and I like Meganium. My favourite is by far Cyndaquil/Typhlosion though. Cute and turns into another beast as with Charmander/Charizard. I never really had that much of an opinion toward Totodile, until I trained him up in Platinum after trading him from SoulSilver, and I have to say, Feraligatr is also really good.
Gen III: I love all of these - my favourite set of starters by far. All three look amazing, and are actually really good Pokémon. My favourite is Mudkip though. It's just so... awesome, and Swampert has a great typing too. Mudkip is my favourite starter overall.
Gen IV: Turtwig is my favourite out of these three. I remember I liked it from when I first saw it, but all my friends were getting Piplup, which I also liked but not as much... anyway, I ended up caving and getting Piplup - but really this was a blessing in disguise, as Pearl was when I only trained up my starter really. By the time I got Platinum, I had learned to train up an entire team as I played through the game and thus it made it more enjoyable. Plus, by then I already had Empoleon (which by the way also has an awesome typing) and I wasn't really bothered by what seemed to be the most popular or whatever (plus most of my friends had quit playing by then)... Anyway, basically, I got my Turtwig and now it's a Torterra and I love it.
Chimchar I never really liked, but Infernape is quite cool. My least favourite of the three though.
Gen V: I have to say, disappointingly, this is my least favourite set of starters. My original favourite was Tepig, but then, we all know what happened after that. Based on just the starter forms, I'd say my favourite is Tepig, but if we're going on all three forms (starter to fully evolved) then Tepig's line becomes my least favourite, and I'd have to go with Snivy/Serperior. Its design is consistently good, and while it may not be that good a Pokémon in itself... none of the three Gen V starters really are, so... I do like the Oshawott line too though.
Gen VI: These three look really promising to me. Chespin isn't really anything special for me at the moment, and I can see a similarity to Oshawott - but, it's the first non-reptile Grass starter, so it should be interesting to see what it turns into. Froakie was a bit weird at first, but it grew on me pretty quickly and I now really like it. Fennekin though - from the moment I saw it I was pretty much like "holy s*** I'm getting that". So yeah, Fennekin is by far my favourite at the moment, and I hope its evolutions are good too. But we'll see what happens with the evolved forms. I'm hoping for either pure Fire or Fire/Psychic (despite all the weaknesses) for Fennekin's final form.
So Fire, Fire, Water, Grass, Grass, and Fire.
Interesting as Water used to be my favourite type. I do love Fire though, and Grass too.