That said, despite dwarves being very powerful in 3rd ed (hard to argue with bonus con and +2 against all magic), they weren't all that popular. Elves are, in my opinion, pretty weak due to their con penalty, but we still saw a bunch of them because elves are cool.
I'd say that game rules influence player choices in the case of the popularity of humans vs nonhumans (say, humans versus elves), but not so much in the case of nonhuman race A vs nonhuman race B (such as elves vs dwarves). Flavour is very important in those cases, since a lot of players who like elves would very rarely play a dwarf.