My conclusion is that some men just aren't very experienced about the range of cock sizes, and have no trouble deluding themselves
That would actually be most men. And most of them in turn are mistaken about the size of their penises in the other direction than you are proposing - thinking they are "small". It seems that there might be more to this story though. The way you tell it, it sounds very much like just a fantasy fulfillment experience for him. It might not have even been one he came up with himself, but rather experienced as the "straight guy" with someone else as a part of their fantasy play, and enjoyed it and wished to repeat it. Or more complicated still, if that had been the case, it might be that he took the impression from that experience that this was normal, or how sexual interaction between men usually went on. Or if that were the case, it might have been that, this was the only way
he could act on those feelings. He might not have been ready to do anything else if he was at the beginning of accepting bisexual feelings, or that he was not interested in much else if he was in fact just straight.
Here is how the game was supposed to play out: He pulls his dick. You turn into the "gay guy", and suck his dick, acting like you really enjoy it. You prop up his masculinity - and his confidence, in either his sexuality, his penis size, his sex appeal, whatever it is. This, I can imagine, would not be fun for you as a regular diet. And it would not be healthy if he were looking for that all the time. Even if you both liked it a lot, and met regularly to play that particular game, what would probably happen? You would either eventually move on to other things - or even start getting attached to eachother -yikes!- or you would both just get bored and stop doing it, the game's function having been served, or its novelty lost.
But you both knew this was just a game. It was probably even expressly a one- time "no strings attached" deal. This is why it is not a good idea to play around with straight guys, definitely not married men. It is too complicated. He was likely looking to act out some "gay guy" fantasty, and you some kind of "straight guy" fanatasy. In the end, he was probably as dissapointed with the experience as you were. Don't suppose I am judging you though by any means. I know how hard it is to have companionship. I think a large part of the function of this site is helping fill that void. Most people, either emotionally or physically, have engaged in something one-sided like this in an attempt to connect, even briefly.
So, with that said, here is what I think. He is actually straight, and you are actually gay. While the straight guy thing can have its cache, ultimately he was probably way to low-speed for you, even despite their being a lack of sympatico between you two. He would have enjoyed it more most likely, with an other straight guy, who was willing to play the "little gay guy" role. (Or else with a gay guy who understood what the game was about, and enjoyed it himself) If he did have a more serious bi streak, he might even at some point been willing to try switching roles with another straight guy. I don't think the guy actually though he had a huge penis. He might actually have worried a lot about it being small, and part of what made the game appealing, was it served as one way (not the best albeit) to gain a positive counterbalance to this anxiety. It might have been a way for him to momentarily step out of his "small penis" role of every day, and explore the "stud role" (maybe critically lacking with his wife) even as much as a step out of his straight guy (real life) role, and into something crazy for a minute. The game wasn't about penis size as all (allthough some games like this are) but rather about masculinity, novelty & excitement, and a sense of being attractive. It didn't matter if you had a big penis or a small one, or your sizes relative to eachother. For the game to work for both of you, you should have just been masturbating, or possibly even flaccid, with all your attention and "awe" on him. (Probably he would have been admiring yours too but, without stepping out of character.) It is not such an unsual game to play, most couples straight and gay, play it to some degree, and when it is mutual and enjoyable for both, there is nothing wrong with it. When games are actually about penis size though, they are usually much bolder and balder than this. For example : 1)"Come fuck my wife Mr. Big Guy please." 2)or simply "Let's compare dicks." Then he admires yours, or you admire his as the case may be. These examples are basic LPSG games, but what you are describing is a lot more complicated, and that's why your story caught my interest.
I hope you are able to find loving and postive interactions in your life as you move forward. Thank-you for sharing this experience!
Once a supposedly "straight" guy wanted to play with me. Our meeting was actually about a fetish-related issue, not one-on-one sloppy wet sex. (He does actually have the wife and kids, but after our meeting, I'm sure he's actually bi, regardless of his self-description.)
He shows up at my place, and takes this attitude like:
Now little faggot, see what a real man's cock looks like.
He proceeds to pull out a very average hard cock. I guess he expected me to drop to my knees in awe and suck it or something.
Unimpressed, I unbutton my fly and pull out my mostly soft cock, which is bigger than his hard-on, despite the fact that I'm not exceptionally large (although quite thick). The dynamic of the situation immediately reversed, and 3 minutes later I was wiping his cumload off my boots. I had a brief fantasy about sending him home to his wife and kids with my cum dripping out of his raw brutalized ass, but just buttoned up my fly instead.
My conclusion is that some men just aren't very experienced about the range of cock sizes, and have no trouble deluding themselves.