There's really no question about whether or not an indoor cat can live a long healthy life; I think from what I've read, and I probably should provide a source but maybe you could just ask your vet--indoor cats do live longer lives and I base this on the hypothesis that if they're indoors, there is less chance for them to escape or be hurt or killed by other animals.
But is living a long life the same as living a happy life? My guess is that it's not and in my opinion, is probably a little unethical/unfair to keep the cat cooped up inside the home his entire life.
Peter is an indoor cat but I make it a point to take him outside for walks or let him hang out on our balcony for some period of time each day. It's one thing to let him bask in a ray of sunshine and watching the outside world through a glass window or a screen door, but it's another thing to be able to actually enjoy the sun.
Peter's a good cat, he doesn't run free and comes back into the house if he gets scared by anything (loud noises from motorcycles or strangers he does not recognize). Because of this, he gets his outdoor privileges and can be on the balcony watching birds and passerbys without me worrying too much.