0th edition (white box/blue box) and its immediate descendants (pink box, red box, and black box/
Rules Cyclopedia) constitute my favorite version of D&D by far.
AD&D 1st Edition is probably my second favorite.
AD&D 2nd Edition would be my third favorite—provided one uses the 1E-style rules for awarding XP (which are optional in 2E).
I don't particularly like D&D 3rd Edition, but I did write up a
recent post here detailing what all I would have to
do to 3E to make it tolerable.
I haven't played 4th Edition (yet), so I'm ambivalent toward it so far.
I greatly dislike 5th Edition.
…Hm. Something of a pattern, that.