I stopped watching the Simpsons after I saw the new opening. Twice as long, and a terrible attempt to fit every character who has ever been on the show in there without reason. We all know these characters if we've watched so much as half a season, and there have been 21 seasons of them. I actually had to remind my mom what 'jumping the shark' means, and how I had just witnessed it first-hand. There's still plenty of the Simpsons that I haven't seen from the 'golden era' and that's more than enough for me.
M*A*S*H is a show I put up as having died at the appropriate time... all we had needed to hear was heard, all the character development we had expected had happened, and all the plotlines had been tied up and completed. Some may say it lasted a little too long, but compared to current standards it lasted a nice, average time. Full-on Goldilocks. Not too long, not too short.