Ten years from now I suspect RoboRally will still be hitting my table regularly. Its been my most played board game for the past ten years and I just don't see that changing. I don't think it'll be considered a classic, but I do think it'll maintain a strong fanbase.
I think it'll certainly be a "cult" classic. It's a love-it-or-hate-it kind of game, no doubt, but it's going to hold up better than games like Wings of War, or lame-ass Galaxy Trucker.
I don't think Descent will become a classic like others seem to. Its in an increasingly crowded field and I suspect the line between RPG's and games like Descent will get crossed even more often in years to come.
The problem with Descent is that it's all over the fucking place. The base game is pretty good the first few times you play, but really, it's not doing anything HeroQuest doesn't, only with a lot of needless chrome and shitty pacing.
Once you get into the expansions, you get a lot more stuff to make the games more interesting, and the quests more distinctive. That comes at the cost of having shit spread out over a bunch of different rulebooks, and the compatability issues. Then you've got Road to Legend, which takes the whole thing and stretches it out to a multiple-session, 80-hour campaign.
Basically, you get all the hassle of playing an RPG, with all the rigidity of playing a dungeon crawl board game. That's great if you're a die-hard Descent fan, and there is the potential for it to become one of those "lifestyle" games, which would definitely make calling it a classic easier. If FFG can continue to keep the interest up, that is.
I'd be curious how well even Talisman competes nowadays. I'm sure its a good seller, but does it outsell Descent, Runebound, and others enough to signify it'll also outlast them?
It's still selling out print runs almost 30 years after it was originally published with no major revisions while too many of its imitators to count have long since been forgotten. Bets don't come much safer.