Bosmer have always been my favorite, hands down. I've tried playing other races and just can't get into it for very long. I love my wood elves!
Orcs are my least favorite but only because a lot of times they seem...out of place. As someone mentioned above, it just doesn't seem right to come across some snazzily dressed Orc selling you housewares in a shop. Not to typecast too much, but really, they're ORCS. There are certain things you just expect of that race and certain things you really don't.
Enough hating on the Orcs! I am here to set you all straight. Orcs have a history if you people are kind enough to read into it. In arena they are EXACTLY like you D&D fools describe, they were hated, outcasts, and enemies. In daggerfall they were building up a structured society system that was very crude, but they were still very barbaric. Now in Morrowind is the time where some Orcs founded Orsinium together and decided that they had enough of the stereotype crap. Other people were very uneasy at first, but soon started seeing their value as smiths. Then comes Oblivion, where Orcs have finally found a place in society that they can call home. Is it that bad that a race got tired of the crap they were taking and decided to bring change? Everyone changes and is different, no one is the same. I have seen many examples of this, too many in real life to count as well. The orcs made a great revolution of their kind just to be hated in the same way they sought to eliminate? No, it is time for all of the other 9 races to stop being over the top racist in their own way and accept them.
Now about orcs selling houseware...would you feel better if it were a white man or a black man selling you houseware? Think of it, it is very racist when you think of it but it is the exact same thing.
And also, Orcs were elves who had their leader eaten by Malacath and cursed, so you cannot blame them for being how they are. I believe that is why they are sometimes referred to in lore as "Fallen Elves".
Now, on the sidenote. My personal favorite is the imperial. I like how I can still feel like myself and experience how it would be like if the world had other sentient beings to live with. I also like Orcs (as stated in my noble crusading statement above) mostly because of their great desire and determination for change ever since the catastrophe that almost doomed them to eternal hate and resentment. I personally believe that all races hold something in them that makes them unique, if we can all look past the obvious faults and see the truth in ones soul.