Not having a lot to compare it with (been with hubby since we were 14... a LONG time!) I can only say what I've experienced. He's average size 6.5 - 7 inches depending on happy I make him, and he's more than enough for me. It's girth that matters for me and that's no problem. Anything bigger and I doubt we'd be quite so experimental.
Have to agree with the consensus that average is just fine, thanks! I do find massive cocks in porn amusing rather than alluring - but then, I guess I'm not the target audience of a lot of porn ;)
One of my current partners is rather larger than average, which took some getting used to at first - he's the first guy I've ever had difficulty deep throating, which he of course thinks is highly amusing - good job I appreciate a challenge!