I played Halo 1 for the first time today. (my experience with the Halo series mainly consists of Halo 3, 4, and Reach) I enjoyed it (though since I'm used to Doom Eternal, I kept trying to punch enemies at the start when I didn't have a weapon, to no avail), though I definitely preferred the first person sections over the vehicle sections. I don't know if it's just me, but the Warthog feels like all of its wheels were replaced with bars of soap.
As a result, I liked the first mission more than the second, since I found it easier to figure out where to go. (once I got out of the cave, I was fine, but the inside of the cave blended together, and it was hard to tell where I had already been since (as far as I'm aware) the game doesn't have a map, just a radar) I'm enjoying the game so far, though, and it's shorter than I expected (ten missions), which will be nice.
I'd be up for seeing Master Chief in Smash. While I'm not sure what all he can do (it's been a while since I played any Halo games), he'd make a ton of sense, especially now that Microsoft content is in Smash thanks to Banjo-Kazooie.