So right now I am playing Need For Speed Hot Pursuit 2 (the 2002 NFS game). I've played through and unlocked everything in it maybe 4 or 5 times in my life. It's not the NFS game I want to be playing though. I'd rather be playing NFS High Stakes (the 1999 NFS game) but the first thing my mac does when I put it in is spit out the disc. I could spend a couple hours trying to figure out how to get a 14 year old PC game to work on a seven year old laptop or I could put a disc in my PS2 and play right away, so Hot Pursuit 2 wins. I have played through High Stakes 8 or 9 times over the years and it is one of my three favourite games of all time. Basically, I return to old NFS games all the time; probably about once every eight or nine months.
Grand Theft Auto is the other stand by for me. I've 100% completed all of them multiple times since they went 3D. I've done it so many times for Vice City that I did it from memory earlier this year with the HUD and minimap turned off. I even return to GTA2 about once a year. I don't know what it is about these franchises but I could take any of their old games and play them today and have a blast, no matter how many times I've played it in the past. Are there any franchises like this for you?