I had both the original xbox and PS2 and I also had a DS and a wii. I spent countless hours playing timesplitters 1-3 and unlocking everything it had to offer, I completed the simpsons hit and run 100% because I felt like it, I enjoyed SSX and SSX tricky, I loving loved halo 2 and CE way too much because of its amazing story that I would re-play any day.
I spent hundreds of hours on pokemon diamond but I spent the most on platinum, I got Giratina, Palkia and Dialga and leveled them all up to lvl. 100. I captured tons of pokemon's and I still play platinum a bit but not very often :(. I also completed mario kart ds 100% just to get rob. On the wii super mario galaxy was loving amazing and I wish I could play that again, I also completed pikmin 2 100% which was also a fantastic game. I completed super smash bros brawl 100% unlocking everything but never played online. I remember on mario kart wii if you completed all the races with a gold you would unlock dry bowser and I did exactly that. I wish games where like this today where you unlock stuff because you achieve more and more stuff.
and on the PC, I spent loads of hours playing UT2004. I loved playing on Faces and skyline, I still have UT2004 and I've spent 25 hours on it on steam and I could play that game any day. I spent hundreds of hours playing the sims 1 and I can still play it, I spent a lot of time on simcity 3000 but when I play that today its really outdated and I just can't play it anymore sadly. I also enjoyed all the valve games. Yeah I had loads of games back then. Now all I have is a pc with a stuff GPU, dunno what I am going to do next