I'd like the guy I date to be taller than me, but I'd be fine if they weren't.
As for size...I think I'd look more at the lifestyle. If the person was overweight but stayed active and would go hiking and do outdoors stuff with me, that'd be fine. If the person was thin but ate nothing but pizza pops and stayed inside playing video games all day, that would be a problem. I'm not overweight, but my body isn't perfect, so I wouldn't expect anybody that I date to have a perfect body either.
As for attractiveness, there are things that are far more important. I like guys that are attractive, but what I consider attractive is probably not average. I've dated guys that my friends considered to be unattractive, or downright ugly, but I thought they were quite cute or handsome. Just having a nice smile or awesome beard is attractive to me, you don't need to look like Brad Pitt.