I've had a similar experience. I'd say very few presets that others have uploaded sound good to my ears when playing solo.
The problem is that most of the time we're hearing it in a recorded mix. The guitars are being mixed in with bass, drums, etc. and there's usually some additional processing done (often compression, limiting, and eq'ing).
The raw guitar tracks will sound vastly different when played out of the mix with no processing. This is often what we hear when we audition others' uploaded presets. Most of the time the tone on raw guitars tracks sounds like utter crap when played solo but once recorded in a mix, "magic" happens and they sound awesome. My presets for recording are very different from my presets intended for solo (practice) use.
We also have to keep in mind that the Axe sounds extremely different depending on what you play it through. Different cabs, monitors, headphones, etc. all have their own eq signature that colors the sound in varying degrees. I haven't come across any sound reproduction equipment that has an absolutely flat frequency response. Some are just more flat than others.
The Axe also shows differences between guitars and pickups better than most other equipment I've tried. With the Axe, I can tell a big difference between tonewoods and pickups on my guitars compared to when I was using a traditional amp setup. This can be good and bad. I like knowing that what I put in = what I'll get out. However, it's made me a lot more picky about guitars and pickups.