I don't really think that's it. He was wigged by the power imbalance in the relationship, but I think there was a lot more to what was wrong with their relationship than that. It never seemed like he was bothered that she was stronger than him so much that he felt generally useless, both to her and in life since he lost the sense of purpose The Initiative gave him. Plus, there was the whole "he liked her more than she liked him" thing. And even if that wasn't actually true (although it really seemed like it was to me) the fact that it felt that was to him created another kind of power imbalance that was a contributing factor.
Personally, I don't think there was anything "closet misogynist" about him. Not to say that he was completely in the right, because he wasn't, but reasons they broke up and his issues with the relationship were more complicated than him simply not liking that she was stronger than him.
I said it "boils back to that." As in, there are other issues, but they all stem from that simple point.
-He was all sad and pathetic that her first thought when her mom was rushed to the hospital wasn't to call him, her white knight. Sorry Riley, but it's soooo not about you right now.
-He cheated on her with those vampire ****es (and yes, that was cheating, I don't care if sex was involved) because "they made him feel needed." Come on, now. If that's not a blatant metaphor for the excuse of actual cheaters, I don't know what is.
-He hates letting Buffy rescue him. He almost let himself DIE rather than let Buffy save him, because the end result would be him being weaker. (Again, Angel never had any problems with Buffy saving his a** pretty much every chance she got).
-Buffy was NEVER gonna be the type to cry into her boyfriend's shoulder. She'll vent to them, or let them hold her, but when she has a breakdown and cries into someone's shoulder, it's Willow's. Yet Riley used that as evidence that she just wasn't committed to their relationship.
-That entire BS ultimatum when he left.
"Say you need me NOW, even though I just did something really horrible and possibly unforgivable, or I'm gone forever. You have 2 hours." If HE was as into the relationship as he claimed, he would have told the Initiative to f*** off and stayed long enough for her to deal with the shocking betrayal he'd just dealt her. Just for the chance that they could work it out. But no, it's her fault, because she wasn't giving herself to him fully to his standards. Good riddance.
-Sure, he'd lost his sense of purpose with the whole Initiative debacle, but so did Giles when he was fired as a Watcher - that didn't cause him to go do stupid s*** to prove his manliness, I mean "worth." All the other Scoobies were fine with being sidekicks. Helping out Buffy fighting evil was purpose enough. Riley still had that need to be an alpha male.
The "closet misogyny" I'm referring to is about expectations: He claims to be ok with having a strong, independent girlfriend, yet he consistently expects their relationship to conform to the traditional social construct that puts the man in the position of strength. Speaking from experience, it sucks.
For other (probably better) explanations, check out the hundreds of comments on MarkWatches' review of "Into The Woods" from not too long ago (you just have to scroll down a tad. I'm not linking directly to the review because there's a great deal of cursing...):
http://markwatches.net/reviews/2012/05/
Riley was the worst kind of a-hole - the kind who genuinely thinks he's "the nice guy." Captain America he was not, imo.