OP here, sorry for the late (and long!) reply, but precisely this. Just because someone's dick is smaller doesn't mean the sex is going to be inherently worse. Are you good with your fingers? Your tongue? Your imagination? Are you adaptable and receptive to new ideas, are you adventurous, do you turn her on? These are much more important questions than is your dick big. Having a big dick is not a pre-requisite for good sex. For me (and remember all women are different) the only pre-requisites for good sex are patience, listening/communication skills and enthusiasm.
For me, clit stimulation is far, far more important (I, like two thirds - 80% of the female population, can't cum from vaginal penetration or have extreme difficulty in doing so). Like I said, this guy has got me closer to an orgasm from PIV than anyone else has but he still hasn't got me there and I don't think anyone ever will. So clit stimulation is far more important to me and, from what I understand, the vast majority of other women, too. And then there are the other factors like mental stimulation, willingness to try new things, eagerness to please, libido etc. If you have a big dick but you're not any good at anything else, it's not going to be good sex, end of story.
In short, big dick doesn't equal good sex and small dick doesn't equal bad sex. Learn to be good at other things (oral, fingering, dirty talk, imagination, roleplay etc) and, most importantly, communicate with your partner. If him and I stopped seeing each other and I found someone new with a smaller dick, whether the sex would still be satisfying for me or not would depend on how the new guy is at oral, fingering and all the other things I mentioned above. Would I miss the big dick? Maybe. Probably. But this hypothetical new guy might satisfy me in new and different ways. Believe me, just because my current guy has the biggest dick i've ever had, doesn't mean he's the best sex i've ever had (he's not).
P.s. As for what I said about his big dick looking amazing, that's much more about domination than visual stimulation. He's a dark skinned black man, i'm white and as pale as a vampire, he's tall and very muscly, i'm 5'3" and petite. His big dick just adds to the way his body looks and feels dominating against mine, and I like to be submissive (lots of girls don't so this won't be a factor for them). It's not like I actually find it aesthetically pleasing, I don't find any penises (or vaginas for that matter) aesthetically pleasing when i'm not horny. It's not what they look like that makes genitals a turn-on, it's what they are and what you know you can do with them.