Halo 3 was much more popular than Halo Reach and Halo 4 and also had a much wider skill gap. I know PC games tend to have much wider skill gaps but I think halo 3 was reasonable, there was a decent skill gap and there was always something to improve upon in terms of individual skill. It was by no means perfect but I think fundamentally it had the right idea and with a few tweaks (movement speed, BR spread, make AR more skilful) could have been even better. Halo 1 and 2 before that were also very popular.
I think the Halo trilogy demonstrates that skilful arena shooters can be very popular on consoles, lets not forget that halo wasn't forced to change, rather when halo did change (dumbed down, class based, COD emulating) it became far less popular.
Halo 4 is just fundamentally flawed, I could never enjoy that game unless it wasn't halo 4. There is so much wrong at a base level, even if you stripped out the gimmicks (AAs, sprint, perks etc) then you have the shooting mechanics which are so dumbed down with the aim assist and bullet magnetism. Probably the reason for slayer pro failing so badly, along with bad maps of course.