I started playing Halo on the release of Halo: Combat Evolved, and have played every Halo release with the exception of the 'apps'.
Halo: Combat Evolved - Every day after school from release until H2's release, with few exceptions
Halo 2 - Got to level 40 on my first XBL account and was banned for superbouncing (I assume, they didn't actually say)
Halo 3 - Got a 47 on Team Slayer, a 50 on Team Doubles, and a 30something on Lone Wolf on my second XBL account and got to 30 something in Team Doubles on my current xbl account. Got banned for trying to derank. .-.
Halo Reach - Got to Noble
Halo 4 - Kind of phoned it in but I got to like SR49. Primarily played custom games and campaign.
The primary reason I'm fine with the way H5 looks like it's shaping up is because Halo is a game that's never the same twice. Don't get me wrong, it's been SIMILAR twice, but overall the series is known for drastic changes from game to game.
When I played HCE using LAN for X-Box and PC, it was really fun. It had more features than most FPS games while at the same time being easy to figure out. Then H2 came out, and I played the crap out of it. Halo 2 was VERY different than HCE, it was like they were cramming as much into the game as they could. Boarding vehicles, duel wielding, and a bunch of other things that weren't in HCE just made the game better to me. Definitely different, but still excellent.
Then Halo 3 came out, and to me and a few other people Halo 3 was kind of disappointing. All they did was take out a couple of features and add equipment, it seemed like. Still fun, but not as fun as H2 for me at least. ODST and Wars came out after that, and they weren't all that bad, but they didn't really feel like full Halo releases.
Then came Halo: Reach, which was really fun to play but frustrated the crap out of me. You see, I'm a campaign/lore lover and it felt as if Bungie was phoning it in lore-wise with Reach to me. Not to mention what Reach did to my beloved Scorpion. Swat and Snipers were still awesome to me though, and I even enjoyed a bit of Invasion, Team Slayer, and Firefight.
Then Halo 4 came out, and it felt like moving from HCE to H2 all over again. Halo 4 had a ton of things that Reach didn't, and I enjoyed it. Not as much as Halo 2, perhaps, but it was still a fun way to kill time. The thing I didn't like the most about H4 though, was that they took the heaping pile of scorpion remains from Reach and somehow managed to make it even worse. >.>
I guess that to me Halo isn't so much about a specific set of controls or features, because I've only seen the game stay even close to the same two times. To be fair though, Halo 2 and Halo 3 were actually originally intended to be the same game but the whole deadline thing... yeah. I digress. To me Halo is a game that changes and evolves. Sometimes it's in a spectacular way (like from HCE to H2) and sometimes not so much (like H3 to Reach). Yet, it's always a good way to make new friends, blow off some steam, and kill some time. There's always going to be features that you don't like, and features that you do like.