Thing was Leela's coma fantasy. Leela assumes Fry's many ex girlfriends would be share her contempt for him as a boyfriend and a lover.
Fair.
The 21st Century Girl was VERY into him, and was slutting herself up in her makeup mirror while waiting for the flying uber. This was not her just going home with the least horrible man on tinder, this was a girl who was very keen to make a good first impression on the boy she was going home with.
I assure you that being extremely into someone and how good they are in bed are not related in the slightest.
Morgan Proctor. Everything Morgan did to pursue Fry and keep their affair secret, and was like a woman possessed by a nymphomaniac alien parasite.
It seems like whatever he was doing was satisfying her, but you can't overlook how clearly she's getting off on a fetish that he's willing / able to indulge. I'd say this is a net neutral point because of that.
Michelle: Liked Fry enough to learn how to emotionally squeeze him into her mindless slave.
I think this would point against Fry being good in bed if anything. He's an easy person to keep around when she needs the emotional pick me up or stability he can provide. The first person we're aware of her cheating on / leaving him for is Constantine. She clearly doesn't hop into bed with him because they have an emotional connection. She doesn't even know his name. She wanted sex and clearly wasn't satisfied with Fry. She goes back to him when she's at an emotionally vulnerable place (frozen in the future) and then ditches him for someone else again as soon as she's comfortable to do so.
Leela: Likes Fry enough to make sure he never movess off her maybe pile and quickly becomes jealous should any woman (or man) make a pass at him. She wants to see other people, but she doesn't really want him seeing other people, unless she approves of the new girlfriend.
This is very similar to Michelle. In fact it's a very common dynamic in general. She likes the idea of the safety net being there for her if she ever needs it. It doesn't mean she's actually romantically or sexually interested in him. That said, we've seen instances that suggest Leela is actually extremely sexually satisfied by Fry (e.g. The Prisoner of Benda).
Amy: Those two could not keep their hands off each other, and when Hermes said "Maybe Fry is a fantastic lover" Amy said, "nope" but her delivery of the nope was very.... ambiguous to say the least, like she was lying, trying not to hurt his feelings... who knows. At the very least.... honestly Fry x Amy was the best pairing I have seen in the show. I'm glad those two kids had fun.
I don't think there was anything remotely ambiguous about her delivery. It seemed completely and utterly sincere and just somewhat like Amy felt awkward to:
1. Have to be putting her friend like that
2. Reminding people that she slept with him
You're right that they couldn't keep their hands off each other, but she says she thought they were having fun together and it seems like there was an element of the fun, exciting workplace romance to it all. She was sad when it was over but also got over it immediately and never once looked back. It doesn't suggest that Fry was an amazing lover who she couldn't stop thinking about afterwards.
It seems Fry does best when he has more woman to work with (similar to Bender) because Fry was pleasing the Amazonians left right and center.
I'm not sure about this. I don't think there's anything to suggest he has sex with more than one Amazonian and it's unlikely any of the Amazonians have much experience with men whatsoever. They also seem to exclusively have snu-snu in a way where the man's involvement is largely negligible. Death by snu-snu doesn't work if you're doing missionary or the doggy position, you know?
I think, in all likelihood, Fry is probably on the bad side of average in bed. It's malleable depending on the joke the writers are trying to tell at the time. He's clearly capable of satisfying people but also not able to do so consistently. To be honest, that's fairly realistic. You can be the greatest lover in the world and simply not sexually compatible with someone. You can be a terrible lover and still occasionally knock it out of the park in a broken clock is right twice a day kind of way.