This campaign certainly ranks high for me; it's the best of 343's work. The mix of linear and open missions works pretty well, and while there's some left to be desired in the way of variety and narrative, it's a strong entry regardless. It's also the most fun I've had with a Halo campaign on Legendary and LASO.

First of all, you need this graphics mod [github.com] to fix widescreen and bumpmapping. Use arrow keys to navigate the menu because the mouse seems to be set to permanent light-speed (probably some engine-baked issue that was never resolved in porting) but in my own experience, setting mouse sensitivity to 1 feels just fine in-game.
Now that those issues are taken care of, the gameplay is plenty of fun. The most important element is your squad commands. Order your squad in effective formations and positions, and the whole unit becomes a murder machine. There's a VERY wide skill-gap between your normal rank-and-file enemies versus the higher ranks, and the way you command your squad is paramount to taking them out effectively. The AI aren't 100% reliant on your commands, however; they do a decent job of taking care of themselves without you, but it's your leadership that turns the squad into something greater than the sum of its parts.
There's a decent number of early-2000's quirks, but the principle of commanding a squad that works together like a well-oiled machine with room for some characteristic banter makes for a one-of-a-kind experience that ABSOLUTELY NEEDS TO HAVE A SEQUEL