I've got them all.

All but H2 for windows.
In order of when i got them:
Halo Demo
Got it thanks to the advice of a Worms 3D player i met on GameRanger, back in 2007. Used to host mods until I said "fuck it" and wanted to make mods myself, and here I am.
Halo: Combat Evolved
Got it for like 60€ (too fucking much) at an apple store. I think around 2008.
Halo 3
A friend of mine got it and we started playing campaign together at his place, and after a while i got an xbox and a copy of it myself. It must've been 2009/2010. I believe i failed a school year thanks to this game too, since i would play it so much. I don't remember how much I paid for it.
It's probably the Halo game I think looked best. Multiplayer was so much fun..! I kinda miss it.
Halo 3 ODST
A title that is kinda looked down upon by most..? But I have loved this game a lot. The story was pretty cool, the gameplay was pretty awesome. I'd play its campaign again if i had the time. I preordered it from Amazon, and it included another disc with all Halo 3 multiplayer maps. That was pretty sick too.
Halo Wars
I think i preordered this one too? The little units were so frigging cute! I remember playing with Fuel and Mota on it, but i suck at this kind of game, i guess? While i'd still farm resources at round starts they'd rush me with their ghosts and infantry. : \ I still don't know how the fuck did they spawn these guys so fast.
Halo 2
Got an used disc off either amazon or ebay for like five euros. It was hella scratched but worked fine!
Playing it made me feel sad that I didn't play it when everyone else did. The multiplayer maps were fucking awesome. Probably the best MP maps of all halos IMO (even if I just played them by myself, since the mp servers had been shut down when i had the game)
The campaign was friggin' awesome too. I guess this would probably be the best title of them all, in my opinion? I might consider getting Halo 2 for windows.
Halo: Reach
The last real halo game. The campaign was awesome too. Too bad that the dialogues were in italian, and translated like SHIT. Halo 3 was translated in italian too and was shit as well under that aspect. But nonetheless, the campaign was fucking moving. If i had not my tear ducts removed i would've shed tears
over all the spartans dying like that. And the end... g-geez.
Halo: Combat Evolved Anniversary
This was kinda unexpected. I've got a friend that works at Rome's microsoft headquarters, he obtained a free copy (i think before the official release too?) and one day he came here and gave it to me and i was like holy shit what omg i love you dude.
It was an interesting restyling i guess. I just don't really like how the look of the game elements changes so significantly in every version of the game. : \
Halo 4
That same friend got a copy for me at like one third of the retail price, so i was like yay and got it.
Just played the campaign in coop on legendary with a friend since i don't have an XBL gold account anymore, and i'm kinda reluctant in giving M$ any more of my money for this. : \ Someday when i'll have time i'll get one of these shitty accounts again and try playing multiplayer, but bleh.
So yeah, TBH I don't even remember much about it right now. : \ I should play it again by myself and watch the cutscenes better, but idk. I guess nothing in this game struck me as awesome or anything like that. Also why is master chief robosexual now?
TL;DR:
Wasted a lot of time on these games. H2 was the overall best, H3 was the most fun, H:R had the most emotional campaign. I suck at HW. ODST was pretty too. H4 and H:CEA were meh.
PS: I tried to keep Johnson alive as much as i could but, yeah, he died a lot anyway. He always seems to come back though? Is he the nigger jesus? I bet two shillings that he'll make a cameo in Halo 5 or 6.
PPS: "nigger" is a term i only use ironically when doing stupid jokes :( racism makes no sense.