What method? IZ3D, NVidia 3D Vision, etc. Passive or active display? TV or computer monitor? What kind of connectors or adapters in between your PC and the display? The software will spit out a specific format native to the hardware.. you can't just tell NVidia that you want to send a framepacked signal, because a computer monitor doesn't know how to decode that. A TV does, but not a monitor.
I'm running NVidia 3D Vision over DVI to a passive monitor. My setup supports 3D at 60fps natively, I don't have to do anything special to make it happen.. it just works that way. So what you're doing is either something very unusual (based on your statement about frame packing), or you've got a bottleneck somewhere that's preventing the system from spitting out a native 60fps signal.
Honestly, the last thing you should think about doing is any kind of conversion or frame interpolation. The results would be horrendous, and the CPU usage would be so high as to render the game unplayable.
Let me ask this: You mentioned "games that run 30fps". Is there a reason why they're stuck at 30fps? Is your computer not powerful enough to push the games at 60fps? If that's the case, then you just need to upgrade your PC. Harsh truth, but truth nonetheless. You need some pretty hefty horsepower to push full resolution 3D at 60fps.
Welcome to Rivendell, Mister Anderson.