It's kind of a useless question to ask, don't you think?
"Forever" is a long time. No mortal can really think ahead that far.
Also, technology advances, and people get bored with their systems, demanding new and improved gameplay and graphics. With that, developers at one point just stop developing games for an old system. A system with no new games is a dead system, so you can't keep buying new games for it forever.
So maybe you should, y'know, rephrase things a little bit. o:
Since I can, however, I'd probably go with the PS2. My decision is based solely on the quality of the games that have been produced over the years. Then again, it woud probably be smarter to go with the 360, but w/e.
You know one of the jokes that made me laugh the hardest in my entire life was this one time when my friend's busted dreamcast was locking up. He looked at it and yelled, "The **** is wrong with you! I hear you spinning! I see your little light on! ****ing DO SOMETHING!"
His brother smacked him on the shoulder, sort of a 'leave it alone' gesture. He said, "Hey! Calm down! It's thinking!"
God damn that was a great machine. Sega needs to come back...