I've been mooching off Digital Press for a couple years now to use the very high-quality Online Rarity Guide. I really never paid much attention to the forums at all until I needed pricing advice on an arcade cabinet. I figured it was mostly the young crowd that ran on forums and I was too old for it. However, so far, I've been impressed with the discussion here and the maturity of both the young and "older" posters on the board. And I've enjoyed participating in it as well... so I guess I was wrong about myself.
I collect basically EVERYTHING hand-held or console from any era. I've played games all my life (started on the 2600), but I got heavy into it around the SNES and PS1 era. I was always casual about games, until 2D and then 3D RPGs really drew me in, and since then it has expanded to all genres (plus I just don't have the time to play many RPGs anymore). I really have no "preferred" system to collect for, although I don't collect too much for systems pre-NES. I guess if I had to pick one I would say that I probably tend to put the most focus on my Saturn collection. I tend to find the systems that did poorly when they came out (like 3DO and Saturn) more fun to collect for than the ones that I already played to death when they were current (like SNES and PS1).
In "real life" I work in law enforcement. However, I sell video games on the side as well (mostly through eBay), but usually only duplicate games and systems that I've picked up in large lots I buy from people in my local area.