Hmm... a pretty tough choice, since I like a lot of the Pokemon Starters... though I probably would have to say...
For Fire, it would have to be Typhlosion. I think its just a cool looking Fire-type, in general. Naturally, there are Charizard and Blaziken following, but Typhlosion takes the top for me.
For Grass, I'd have to go with Sceptile. It had so much potential of being a Dragon type, as well, but I guess its for the best that its pure Grass, seeing as it would have been adding to the x4 weaknesses that other Dragons have, lol Following Sceptile is Venusaur and Meganium, who just miss out on a top stop from me.
For Water, I'd say that Swampert takes the glory. I originally didn't like Swampert because of the annoying "Mudkipz" I kept hearing and seeing on the Internet, (what DeviantART did with peoples' avatars I think last April Fool's was what tipped the boat, really) Swampert has broken the ice on that lake and actually is an active member of my team. I still dislike Mudkip, though...
Following up would be Feraligatr and Blastoise; as with Venusaur and Meganium, just running shy of a top spot.
This probably differs from what I had last time, (I'm sure there was a similar topic, waaaay back when I was active, last year) but my opinions on certain Pokemon have kind of changed; the most radical being Swampert, who I'm pretty sure I had in dead last.