I'll only comment on the editions I've actually played
>AD&D 2E
If you want crunchy, but gritty and realistic but still magical medieval adventuring, look no further. Boy does it have its problems, but it's fun, even beyond the nostalgia factor
>3e/3.5/PF
I can't say I enjoy playing this game, HOWEVER, building a character in the game is REALLY fun. It's fun enough to be a game in and of itself. It gives you the same satisfaction you get after building a top tier deck for a CCG. Much like building a top tier deck, playing quickly becomes dry after you've seen your gimmick/combo "go off," but DAMN if it isn't fun to build.
>4e
Combat is fun enough to be a game in and of itself. Crunch is not tied to fluff, so re-fluffing is the easiest thing in the world, making countless character concepts that once were not possible possible.
Similarly, it is the easiest edition to DM, requiring almost no prep time, and is, by m count, the only edition of D&D ever to have a functioning encounter balancing mechnanic that makes hitting the sweet spot between "party uses no resources" and "TPK, everyone go home and stop having fun with your friends" easy.j Just like with character concepts, the seperation between fluff and crunch means you can throw literally ANYTHING at your players by a quick re-fluffing and elemental-damage-type switch-out
>5e
It plays pretty much like 3e, but with duct-tape. This makes it kind of a middle ground. It's easier than some others to DM, but not as easy as 4e, because it requires much more prep. It's fun to build, but not as fun to build as 3e, because there isn't quite as much cheese. The adventuring realism is there, but not as good, because it's not nearly as crunchy. The only thing it's the BEST at is ease of finding a RL game. Personally, I just don't care for the game at all, but I guess I can see how it's something everyone can agree upon... Dennys for D&D: you can always find one that's open, and while it's not BAD