I'd be more impressed by quality over quantity. If someone had 1000 games that were the best and most interesting titles across five platforms, I'd be more impressed by it than by the collection of someone that managed to get, say, all of the USA Sega Genesis releases. I understand the appeal of collecting an entire set -- not unlike a full set of baseball cards or a full run of a comic -- that feeling of completion and accomplishment is nice.

However, if you have a room filled with fullsets, then odds are, you also have a room filled with at least 60% crap or mediocre games, and you're stuck with all of them, because as soon as you get rid of a couple titles you no longer can make the claim you have a fullset. With a really quality collection, though, you can always selectively pare it down, swap out games as your interests changes, and not be trapped in essentially having a warehouse for a living space.