Something like 80% collector, 20% gamer, trace amounts of reseller. Like a lot of folks here, I can buy a lot faster than I can play, so my collection definitely outpaces my completion rate. I always refer to my set as a 'working collection' though- as in, I want it to be used. I will lend games out to friends, I'm fine with my nieces & nephews using the systems (although I do try to focus the 2 year old in on the nice, durable Nintendo stuff). It's there to be played, even if I'm not the one doing it.
As a general rule, I don't resell anything. If I have a double of something or a game I don't want, I'm a lot more likely to give it away than sell it. I have done a lot more of it in the last year than I have in ages. A co-worker told me last year how badly she wanted an NES for her husband's birthday, so I sold her my old loaner console (since no one had borrowed it for a couple years). I've also recently gone through my Genesis/NES/SNES collections to remove sports & licensed titles I don't play. This has resulted in 1 (now closed) sales thread on another forum, 1 eBay sale, and 1 box of a dozen games of undecided fate. Once those are gone, I don't foresee anything else getting sold for another several years. I may buy faster than I can play, but I am picky about what comes in- if I buy it, it's because I want it here for good.