The A-1 answer to this is always humans. Humans play humans more than any other race, which is hardly surprising.
What interests me is the loyalty many players have to a particular race. People find some races viscerally appealing, and others repugnant.
For instance, I like Tolkien-style halflings and loathe the 3E pseudo-kender. Hobbits combine the sense and versatility of humans with a convenient, hideable humanoid form. Of course, many people find them bucolic, homely, and intensely boring, and are delighted by the "exciting" new halflings. I understand that, but I still feel you could replace kender-halflings with a race of gutter-dwelling ADHD rat furries and the only essential difference would be a marginal increase in cheese theft.
I've tried, but I can't get enthusiastic about dwarves. In fantasy they've come to be a staid and narrow-minded race, which I don't find appealing. On the other hand, they're loveable for the same reasons dogs are: commitment, consistency, and undying devotion to their comrades. But short, fat, gruff, dogmatic and parochial are just too many ticks in the "cons" column for me.
I've never seen an elf who picks his nose and leers at women. In fact, the only times I've seen an elf who wasn't a shining, flawless super-human was when an elf-phile deliberately played a short-lived "bad elf" as a caricature. That, alone, is why I've come to hate elves: they end up being an ego soak for people who want to play an angel, instead of a well-rounded player character.
Oh, and now that I've sullied the OP and half the gaming community with a spray of foam-flecked criticism, my favourite race is hobbits.