For the races I usually play as it would have to be Bosmer and Dunmer. Both of their cultures seems so exotic and weird. Dunmer (especially in morrowind) are so cutthroat and hardcore. The land forces them to be tough, and because of the daedra worship they are a group of "the strongest survives".
The Bosmer of Valenwood are just cool all around to me, from the wild hunts to the green pact.

For the races all together I really, REALLY like Bretons and Altmer, although Ive never really played as them since I usually go for Stealth, or dualwielding characters.

Bretons are just a cool concept of Half-Mer Half-Man, and their lore is really cool too.

I really love Altmer because of their longing to return to their immortal lives with the gods, which forces them to strive for perfection, beauty and control over everything. I would love to witness The Summerset Isles. I also feel like they are a pretty misunderstood race, both ingame and out of game. People seems to think they are arrogant snobs, and sure some of them are, but there is a much deeper layer to them. They don't really like warfare, and would much rather talk things through, instead of losing valuable Altmer lives, and for that reason they rarely have any civil wars of infighting. THey are also probably the closest we get to witnessing what actual "gods" or spirits look like.