It varies by the generation, though with generation three, four, and five, I had to have the fire starter. :P
Kanto: Bulbasaur. Though I love all three, Bulbasaur was the most logical choice to me (even at 10 I was a little pragmatist). First gym leader? Brock. What's Brock use? Rock/ground. BAM! Instant advantage. Second gym leader? Misty. What's she use? Water. Bam! Instant advantage. Third? Lt. Surge. What's Surge use? Electric. Grass resists Electric. By the time Sabrina and Blaine roll around, I have things to cover them. Koga loses some damage against the 'saurs since they are part poison themselves (plus, you should have a Kadabra by then, or, if you're me, your Hitmonchan just burns through them with Fire Punch).
Johto: I love Cyndaquil. Even though I liked Totodile, I wasn't crazy about its final stage and just plain didn't like Chikorita.
Hoenn: The beginning of an annoying trend. I am a fighting specialist, and, as such, must obtain all fighting pokemon. I really don't like Torchic and Blaziken (though I like Combusken), but I had to pick the stupid chicken even though I wanted Mudkip. Never really cared for Treecko.
Sinnoh: This crap again. Though, to be fair, I didn't like Piplup (too cutesy and I didn't like its final stage enough to deal with that) and hated Turtwig. Chimchar is cute, but I still didn't like the feel that I had to take it. Even so, come Dec. 27, Hephaestus is being moved right into my team.
Unova: This really irked me. I absolutely hate Tepig and all its evolutions. I wanted Oshawott, hell, even Snivy would have been acceptable.
Kalos: Just like in the Kanto, I love all three starters. Chespin? Adorable. Froakie? Adorable. Fennekin? Adorable (though to a lesser extent than the other two). I was so relieved that Fennekin's final evolution was Fire/Psychic and since I liked Chespin the most to begin with, I was happy to choose it.
I will be on here very, very rarely. The account is not dead, per se, but I will not be on often. This has become a den of hatred, hostility, and anger. It is not the SPPF it was when I joined, and I really dislike coming here. To those of you who were nice to me and were my friend, thank you. Goodbye.
3DS FC: 1950 7837 2016
Electric Friend Safari. Pokemon: Dedenne, Pikachu, Manectric
Before you try to act superior to someone else on here, remember that no matter how much of an "internet cool-guy" you think you are, this is a Pokemon forum.