I picked Piplup in Diamond and Platinum, Turtwig in Pearl, Totodile in HeartGold, and Cyndaquil in SoulSilver. I picked Piplup in Diamond because I always start my main game with the water starter, and I picked it in Platinum because I liked it a lot in Diamond and wasn't that fond of Chimchar (don't like monkeys too much, though it's grown on me with time). I went with Turtwig in Pearl because I thought it was cute, liked turtles, and liked the idea of a grass/ground starter. In HG, I chose Totodile because that's what I used in my original Gold, plus, as mentioned before, I generally start my "main" game of any set of games with a water starter. I went with Cyndaquil in SS because I've always liked Cyndaquil and because I used it when I first played Silver (a while after I got Gold).
I've never really used Chikorita. I've always thought I should try it as a starter, but I guess I just like Totodile and Cyndaquil too much. It's kind of like how I always choose Squirtle when given a choice of the Kanto starters because I like Blastoise so much (though I've incorporated the other starters into teams later by trading).