Hard to say, they all have their strengths and weaknesses.
- Halo: CE had an amazing campaign, and the multiplayer was good but no online and the pistol was super overpowered.
- Halo 2 had amazing but limited multiplayer, however I didn't like the campaign as much as CE. I also had a lot of fun with all the glitches in this game.
- Halo 3 introduced Forge and Theater modes to multiplayer which was amazing. I don't think the multiplayer gunfights were has good as Halo 2 though. The campaign was very well done, and the 4 player co-op was a lot of fun.
- Halo: Reach had a really good campaign as well, probably better than 3. My favorite part about reach was how expansive the forge was compared to three, however I really didn't like the gunfights due to bloom. Reach's firefight mode was alright, but it was way better in ODST.
- The only thing I liked about Halo 4 was the improvements to the forge. I didn't really care for the campaign and the class-based multiplayer made the game feel like CoD with a higher TTK.
- I can't speak on Halo 5 because I haven't played it.
I would say Halo 3 is my favorite. As much as I enjoyed super-bouncing in Halo 2 and exploring outside of maps, it was Halo 3's forge mode and campaign that I enjoyed the most. Also infection as an official game type was loads of fun as well.
- Halo: CE had an amazing campaign, and the multiplayer was good but no online and the pistol was super overpowered.
- Halo 2 had amazing but limited multiplayer, however I didn't like the campaign as much as CE. I also had a lot of fun with all the glitches in this game.
- Halo 3 introduced Forge and Theater modes to multiplayer which was amazing. I don't think the multiplayer gunfights were has good as Halo 2 though. The campaign was very well done, and the 4 player co-op was a lot of fun.
- Halo: Reach had a really good campaign as well, probably better than 3. My favorite part about reach was how expansive the forge was compared to three, however I really didn't like the gunfights due to bloom. Reach's firefight mode was alright, but it was way better in ODST.
- The only thing I liked about Halo 4 was the improvements to the forge. I didn't really care for the campaign and the class-based multiplayer made the game feel like CoD with a higher TTK.
- I can't speak on Halo 5 because I haven't played it.
I would say Halo 3 is my favorite. As much as I enjoyed super-bouncing in Halo 2 and exploring outside of maps, it was Halo 3's forge mode and campaign that I enjoyed the most. Also infection as an official game type was loads of fun as well.
