How long do warm water fish (aquarium) live?

I got an aquarium for Christmas like 3 years ago now and I bought fish right after. I had six little guys in this huge tank. Over the next year they all died except for one. They had a disease (ick) and some survived, others died a bit later. The ones that were first to go were Tiger Barb Tetras a href="http://animal-world.com/encyclo/fresh/cyprinids/images/TigerBarbWFCy_C2593.jpg" rel="nofollow"http://animal-world.com/encyclo/fresh/cy…/a and the ones that lived longer were Black Phantom Tetras. a href="http://animal-world.com/encyclo/fresh/characins/images/BlackPhantomTetraWFCh_C2464.jpg" rel="nofollow"http://animal-world.com/encyclo/fresh/ch…/a I cleaned the tank real well and bought more fish to the tank, both the same species and again, all but one (same black phantom tetra) died. I tried this a couple times and all the other ones died except for the original black phantom tetra. What the hell? It's been three years and I'm not a great fish keeper... this fish is still kicking it back alone in his giant tank. Why will every fish die except for him?