I'm going to say hot. And not just to be contrarian, I did take the time to think it through.
Firstly - when I was 17, I fancied 17 year old girls. I often worried whether that meant I'd still fancy them by the time I was 25, but luckily, age changes your perspective on younger people, and now I see teenagers as annoying, ugly children. Cullen, on the other hand, whilst being 100 years old, hasn't physically matured beyond 17 and might not have aged mentally either. It's more like he's frozen at that age, rather than actually getting any older, so I rule out the paedophile factor fairly quickly. Besides - if we go by the logic that the age gap makes him a paedo, every vampire would be too; Dracula has centuries on all the women he dates, and I certainly don't see him chasing down septuagenarians. I do think Cullen is an idiot for doing nothing but going to school for 100 years, or for not have sex at any point throughout that time period (which feels bad enough when you're 17), but I don't think it is inherently creepy.
As for the stalking and watching people whilst they sleep...all right, that is creepy, but he's a fucking vampire! If that's the worst he does with his spare time, we're getting off lightly. I don't think it is something a woman should typically find romantic, but romantic fiction logic always has a bizarre perspective in general: lots of things are treated as sexy which would normally be considered horrific, unpleasant or illegal. How many romantic bodice ripper stories are there? Mills and Boon practically run off of the philosophy that you can't have a romantic relationship without some hunk date raping the protagonist. Even Jane Eyre had bigamy, stalking and a highly romantic blinding-after-saving-pyromaniac-first-wife-from-a-burning-mansion scene (oh yeah, spoiler warning). I think we can accept that a lot of people like to reinvent sex crimes as a romantic fantasy, so I'm willing to let the stalking thing go.