Yes, looks play a large roll in the initial stages. Men are visual creatures. Yes, other things can occassionally supercede the physical attraction factor, but I would surmise that this is the exception rather than the norm.
Looks play a large roll in first becoming interested in a woman romantically, the rest of the stuff - humor, intelligence, affection, etc. - play into whether that person will work out romantically in the long run.
Luckily, guys have wide and varying ideas of beauty.