As with most things in life there’s a distribution of sizes and preferences. I’m pretty average at 6.25 inches long and average girth and for several of my partners I’ve been slightly too big, especially when being vigorous. On the other hand several of my girlfriends have enjoyed great sex with me, cumming six or seven times per event, but have enjoyed even more intense sex with larger guys, cumming a dozen times or more per event. One of my partners discovered she could take the really massive guys (she measured one at over 12 inches in length and much wider than she could get her hand around) and it was amazingly pleasurable for her. The variability of a woman’s vagina is no less than the variability of a man’s penis, and getting the “right” match is definitely a good addition to everything else (emotional connection, compatible preferences, etc.).