That's a hard one. If we're looking just at the physical, then it's Seven. Hands down.
But, I find it hard to just look at the physical. When I'm considering how attractive I find someone, then I need to look at a lot more than the physical. Personality, strength of character, how they move and express themselves etc etc.
Janeway can give me the shivers, but Seven is classically more beautiful.
Except when Janeway smiles - Mulgrew has a beautiful smile.