Anyone else do this? I do it waaaaay too often.

The only way I would is if I thought that it was actually pretty good back when I originally played the game. I've done that and sometimes the game is still pretty awesome but a lot of the time, it's pretty terrible and I'm disappointed because of it, haha.

I never buy a game that I do not intend to play.

Well, for my favorite games from the past I sometimes re-buy them for new consoles. And if I really like a game from current gen I may buy it for more than one console.

Yeah, I have all my old (and often pirated) games bought and sitting in my nice Gog shelf. Most I have started up, played a bit to get 'that' feeling again, to quickly decide that it was fun and I should play something modern. But it's a nice thought you can look at them when you want to :-)

gog.com is the best/worst thing to happen to me. So many games I played at friend's houses, or had been loaned, etc... and never played all the way through.
I end up buying them just because "Oh hey, I remember that game!" and mostly waste money because there's no way in heck I'm gonna find time to play them all again. However, I still buy them (on sale at least) in case I find that time one day...

Most of the games I have I fully intend to play. Saying that, I rarely have time to play too much so a lot sit staring at me for not playing them. I get them from GOG, Steam, Humble Bundle. Due to HB I have gotten a few Origin games though. Most of the old games I have I kept from back in the day. One of my old favorites is Sam & Max Hit the Road. I have it on CD and I have the executable from Lucas Arts that made the game work great in Windows and smoothed out the graphics. Glad I have that still so I don't need to get it from GOG, which does not have that exe file. I think the GOG version uses SCUMM. :-)

I've got it double bad. Not only do I have the standard nostalgia, but I actually lost a lot of physical games because I was in Korea, lost one job, thought I secured another, and put most of my stuff into storage, only to have to abandon my storage when the job fell through.

So now if I see a game I had before (and had at least played a little), I'm very tempted to pick it up. Luckily there are times when doing so is actually pretty cheap, such as Steam recently having Ghostbusters: The Video Game and Virtua Tennis 4 for $3 each.

Yeah and I enjoy the hell out of them.

did it with Apogee Raptor :D

Yep, way to often.
Even yesterday was looking through ebay and stumbled across The Lord of the Rings: The Third Age And The Return Of The King for the PS2,
ended up grabbing them just because of how much fun I remember having playing them at a friend's place.

I accidentally buy Sonic Adventure 1 or 2 at least once a year in some format just because of the amazing childhood memories that game gave me.

I've double bought one or two things on GOG that I already own on physical media, but mostly I don't. There's also some things I'm at least considering getting on GOG because the DRM/copy protection on the disk renders it borderline unplayable today, for example because the copy protection only works properly on 9x or XP.

Then there's all the games I buy that I never owned, like Wolfenstein 3D. The demo came included with Terminal Velocity. I played that for a couple of hours in ECWolf and I thought it was definitely worth it. That describes most of those ~€ 2 purchases. Slightly wasteful perhaps, but surely no more than how some people visit a bar all the time or something. :)

Definitely. But mostly because I am in process of replacing games that recently (in the past couple years) disappeared.

Then there is the NES... I've always wanted a complete licensed set.