I think Halo get's loads of flak for creating regenerating HP, but also for it being and exclusive and Microsoft flagship.
I think Halo ironically, is one of the less generic shooters out there, as it's gameplay is like no other shooter out there, and the world is substantially different.
One of the main point people pull up is the regen, but what other game uses the EXACT same health system as Halo, COD, nope head shots kill you instantly. Don't get me wrong, it did start the regen trend, but not many games if at all are willing to copy it in the same fashion.
The main thing that I only see as generic is the characters, but this was because they were one of the originals.
One thing that I would like to add is that each of the 3 main halo games, have added something that was evolutionary or perfected to the gaming world, such as the health system, multiplayer, and forge.