I loved the deployables in Halo 3. They gave players interesting options, and they were more about utility (like flare, grav lift, and cover). In order to make them work, you had to figure out how to use them properly. I've enjoyed pretty much all changes Halo has made. Maybe what I enjoy about the series the most is simply the engine, rather than the content. I liked dual wielding in some of the games, armor abilities in Reach, I liked ordinance in 4, I like boost shenanigans in 5.
I like equipment for non-competitive play like H3 did, but everything else he said physically hurt me.
I gave my vote to Halo 2. I am a big fan of the original trilogy and my best memories were from H2. I can't really comment much on the games after that. Once Forge came out I didn't spend much time in the other parts of the games. H4 looked pretty but I bailed after the 1st couple campaign missions. Only thing I really liked was trolling with the sentry equip. I loved the story of Reach and the world it built but besides that I'm all about the trilogy.
I played H2 a bit at my friends house but my first real Halo was 3. Love the game, everything except for the bumpy movement prefer H2) and the fact that I never really feel like I'm hitting someone when I'm shooting them. I loved Reach, as it was my first introduction to the community, loved forge, loved customs, loved BTB and Invasion, was too much of a casual to know what the word 'unbalanced' meant. Looking back now however... yeah, it was unbalanced in regards to the class system and abilities. Halo 4 came around and like everyone else... there was just something that didn't feel right. I thought the abilities were pretty much ass except for the little Knights shield. I actually really liked that little shield, and I'm happy that something similar is in the more recently released Star Wars Battlefront 2, because I honestly kinda missed it. I feel like the MCC fixed the H4 multiplayer though by essentially removing the AA's or allowing you a very limited amount, such as just the shield. With those gone, H4 is actually one of my favorite games to play in the MCC playlists. For BTB at least that is. I loved H5 at first... but it's begun to wear on me recently. I find myself more entertained by gunfights in H3 and 2 then I do in 5, which I find strange considering all the Spartan Abilities should add extra variety for more interesting engagements... right? It's just begun to feel over saturated, and I've found myself returning to games that feature the good ol' 'boots on the ground' gameplay instead. Also, love Halo 5's forge, and while it was a huge step up for forge, I still think its a long shot away from being considered a great map creator. Comparing the way H5 does foliage to how Farcry does foliage is enough to explain my perspective. Overall I've enjoyed each Halo and have never out right hated what any of them have brought to the table. Only over time have some of the features presented in the franchise begun to wear on me. BIGGEST PET PEEVES -H3 movement -Reach Unbalanced Class/Armour Abilities -H4 Armour Abilities, and that one BTB Ravine map that shipped with the game -H5 Spartan Abilities (Loved them at first, now they make me sick) Ultimately I voted H3. Just can't deny how solid of a game it is, and my nostalgia helps me see past the movement issues.