Well, personally, I went with Cyndaquil. But thats mostly just because I like fire types and find them to be pretty useful. Also, it has been my experience that there are generally way more water types and grass types to be found throughout the game than there are fire types. I mean I've filled a whole storage box with water types in HG, and my grass type box is about 2/3 full. I've got 7 fire types total right now, including different evolutions of a few, and Ho-oh and the big fire doggie (Entei). Granted I haven't evolved my Slugma yet, but it does seem to me that fire types are a bit more rare than other types.
As has been previously discussed, each of these types (fire, grass, water) have their own strengths and weaknesses (just go ask Professor Elm). And each of the starters is fully capable of becomming quite powerful depending on their level and what attacks/moves you teach them. So, it seems to be to be rather spurious to claim that one or another "sucks". All things being equal, any one of the starters will be somewhat effective against the others. Tell your friends they are ill-informed and their arguments are without merit. (If nothing else you'll sound much more intelligent than them.)
And I really love Typhlosion's alternate coloration! That sprite is amazing as well.
