I flew with both EasyJet, Ryan Air and GermanWings. Of the three, German Wings was by far the most superior LCC. Easy Jet from Athens to London (Gatwick) was great, too. If you can get emergency row seats, it's even better. Ryan Air from Paris to Barcelona was not that great, as the plane seemed very dirty and there were a lot of annoying Samsung ads in the plane, a la metro/tube kind of ads. The flight on Ryan Air from Barcelona to Rome was good, though, so it probably depends on the route.

In either case, I'd much rather fly LCCs in Europe than pay a lot more to fly marginally "better" (if that's an appropriate term) legacy carriers like BA or Lufthansa.