I'm with you. To me the biggest innovation (besides console mp) was getting fps controls right for gamepads. I also like that it popularized a limited weapon carry. Health regen is a mixed bag for me, and it definitely got overused in other games of that era.

If I didn't have a PC at the time, I could see myself enjoying Halo more. When I got around to playing CE on xbox, I was underwhelmed. I thought Halo 2 was more fun, but the pop-in was so bad I think I skipped all the cutscenes. Like you said though, the mp was always a blast.