It really depends on many, many things. Surely you can sit through the most lengthy piece of work ever created and have an aneurysm while doing so if the substance isn't up to par. And yes, a very short piece like Portal can keep you referencing the witty dialogue, plain fun mechanics, and so on... for years.
However, keep both length and life in a game, you've truly got something special. On a sadder note, it's my depressing opinion that the game industry is somewhat leaning towards music, releasing piece after piece and leak out as much material as possible, however bland and unsatisfying, just to bring in as much loot that they can get out of the poor-tasting masses.
In short, quality is quite better than quantity, in my opinion.
However, keep both length and life in a game, you've truly got something special. On a sadder note, it's my depressing opinion that the game industry is somewhat leaning towards music, releasing piece after piece and leak out as much material as possible, however bland and unsatisfying, just to bring in as much loot that they can get out of the poor-tasting masses.
In short, quality is quite better than quantity, in my opinion.