It's just getting old, hardware doesn't last forever it can become stressed and deteriorate. My PS2 (generation 2, about as old as it gets) will play PS2 games fine (unless they're blue backed) but it will take upwards of 45 minutes to load a PS1 game. It still works with all games some just take a super long time.
your laser is out of focus (its called v9 syndrome). you can fix it yourself if you dont feel like risking it with some asian guy in a corner market for $50 bucks.
http://arstechnica.com/articles/paedia/hardware/ps2.ars
good luck if you go for it