Every edition of D&D besides 3e/3.5 (and maybe 4e, I don't know as I haven't played it) has been at LEAST decent.
>OD&D is a fantastic dungeon crawling game and serviceable for other things as well
>BD&D has some of the most fun settings ever published, and is good as a system
>AD&D 1e is probably the weakest TSR D&D system, I would say, at least played as-written, but it introduced the DMG and isn't a bad game at all
>AD&D 2e is great, and the worst thing I can say for it is that the non-weapon proficiency stuff started getting out of hand, leading to the skill system we had later
>D&D 3e/3.5 is playable with the right players and a DM willing to carefully select which classes are allowed and possibly some houserules, but I think that can be said for ALMOST any system, so I don't count it as a point in 3.5's defense
>I haven't played 4e so I can't say much about it
>5e is pretty flexible as far as what kind of game you play with it, is miles better than 3.5, and seems much less controversial than 4e