Usually the third person, but sometimes first person can be nice (as with Lestat and Louise in the Vampire Chronicles). I remember reading second person back when Goosebumps was popular (the "chose your own advernture" ones)
I think it depends on the novel. Some books just don't lend themselves to the first person and some would be rubbish in the third person. Either is good as long as it's right, it's amazing how many writers get it wrong
I prefer to read a novel in the third person, but couldn't actually tell you why! I think it is somehow easier for me to visualise what is happening, the setting, etc.