Sony didn't support the ps1 very long after the ps2 launched. It stopped selling well pretty quick. They support the ps2 because the ps2 and its games sell better than the ps3. The ps2 is the only reason sony's doing as well as they are.
However, i'm going to defend sony here just a little bit. They're finally getting some games out worth owning. MGS4, disgaea, valkyria chronicles (this game is extremely fun), Resistance 2 to an extent. Sad I bought the CE myself. =( I think R2 sucks compared to gears but that's another convo entirely, and it's obviously up to opinion. Motorstorm now has a sequal with local 2 player support, which I know will bring it a lot more sales than the first one did. That was the only thing keeping me from owning the first one personally.
The problem with saying they're gonna be the top system though, is the 360 simply has a stronger lineup. Way back I wanted to own a ps3 because I thought that sony would be the rpg console once again. Now? You're kinda nuts if you love rpg's and don't own a 360. Even that is beside the point though. Neither system is going to top the wii this generation. Maybe next generation. I know there are a ton of people out there who are tired of the motion controls. Especially considering they don't work half the time.
