Human, Dwarf, Elf and Eladrin
(for 4E newbs, the Elf is your old Wood elf variety and Eladrin are High elves)
It would be interesting to see what the fifth most popular race is, but whichever way you turn it, it's clear that the classic old triad of Human-Elf-Dwarf is and remains the most popular by far.
The most popular class is...*drumroll*...Fighter. No matter how many cool new options and classes, divine, arcane, shadow, psionic or whatever heroes they offered, the Human Fighter remains on top. Pretty interesting.
The least popular class is the Runepriest. I even forgot that existed. I don't even know what it is. I guess it's just not appealing.
It would be nice to see WotC release more of this info.