Best race: tier'dal. Same as for every class. We're just flat out the best race in the game. Sorry to all you losers who didn't pick a dark elf.

Best stats: depends on how you see yourself playing the character.
INT - best stat for magic damage, which is ultimately our best damage source.
STR - best stat for melee damage, a small component of our overall DPS but one which can be used more universally than mental damage (the ONLY non-physical damage type we deal) thanks to auto-attack.
AGI - best stat for power (Int is roughly 1/3 as good for power, will soon, apparently, be about 1/2 as good) and defense (avoidance, really) - critical at lower levels, less so in raids, and good for solo/group at any level.
WIS - good for resists and that's about it. Nice to have against caster mobs, especially debuffers and mez/stunners, can be critical in some raids.
STA - mediocre stat generally - an extra 60 stamina at level 60 yields a few hundred HP, which in most cases amounts to less than 10%. Our regen typically is the solution to any damage that doesn't one-hit us, so stamina is far less worthwhile than to most classes.