I have a soft spot for D&D, dating specifically to the AD&D era. But I’m not sure it was ever my “favorite” so much as it was “the game we’re playing”. I had a ton of fun with AD&D, particularly AD&D2, I had perhaps even more fun in a long-running D&D3E campaign (though the rules were a constant source of frustration and annoyance). I still love the style of play that D&D engenders, and want to do it again, but I don’t particularly want to play the game that says Dungeons & Dragons on the cover any more. Certainly not BD&D, AD&D1/2, D&D3[.5]E, or D&D4E; maybe D&D5E (though I suspect once I’ve tried it out, I’ll quickly discover it’s not the game for me any more, either).
So, no, D&D may be a game I no longer play (though I’d like to), but I don’t think it was ever a favorite.
Now, there are several games that truly are my favorites, but which I haven’t played for years. But several of them are games that I still would play, and know people who still would play, so the only thing stopping me is a lack of time. I don’t think they qualify, either.
Probably the closest I can come to a game that legitimately qualifies as a favorite, but I strongly suspect I will never play again is Werewolf: the Apocalypse. Partly, it’s a badly misunderstood game—and White Wolf’s advertising didn’t help matters. Most gamers I’ve met who like the old World of Darkness games weren’t interested in a “hack-n-slash” game, and completely missed that W:tA isn’t about triumphant combat—it’s about tragic characters whose favorite tool is ultraviolence faced with situations that can’t be solved by violence, set against a backdrop of a crumbling world that they created precisely by their misguided applications of violence to attempt to fix it.
Even with the right sell, the number of people who want to play tragic shamanistic warriors with anger-management issues up against impossible odds is, apparently, pretty small, and the few who want to either are put off by the fact that they’re also werewolves, or are more interested in LARPing (at least IME).
Additionally, my mechanical tastes have changed. I still love the characters and setting of W:tA, but I’m no longer interested in chapters of martial arts maneuvers (unless I’m playing a martial arts game), and I either want a system with self-evident extrapolations from the basic mechanics to specific detailed rules, or a system where there are no detailed rules. The oWoD games unfortunately are riddled with almost-arbitrary implementations of the core die mechanic to get the specific “systems”, and the Gifts (and equivalent powers in most of the other games) are just about the textbook example of rules by exception.
On the flipside, I love the detailed setting, and part of what makes it what it is are all the nuances of the Gifts and the various tribal differences, and the wyrm taints, and so on. Converting it to another system while preserving most of that detail would be more trouble than it’s worth.
Finally, my current circle of gamers is generally not interested in games of this level of mechanical complexity, period, and most don’t have the time any more to read chapters of setting just to play in a world—much less to make characters. We generally prefer building our own settings or playing in genre pastiches, these days. Myself included. So despite the awesome times I had playing (well, running) it, and how much I absolutely love the setting and even the game as a whole (despite my misgivings about some of the details of the rules), I think maybe it is better left in the past. I fear that playing it now would tarnish my memories, rather than rekindling my love.