I'm not that big, but all the guys I've been with have been a bit smaller than me. I've had no complaints. Actually, I'm not that good at oral sex, so I'm not sure I'd be able to handle a bigger guy.
I hate to say it, but I'm not sure if I'd be happy in a relationship with a guy who was a lot bigger than me, for the same reasons I wouldn't want to be in a relationship with someone who was much better looking. I have a tendency to be self-critical, so I susect that I'd be prone to comparing myself unfavorably to my partner, which wouldn't be healthy for either one of us.
Nevertheless, I've always wanted to have sex with a guy with a genuinely large penis. I've seen so many in pictures, I'd really like to see one up close and personal.