Unfortunately you cannot use vlc to do this. So go get yourself a copy of virtualdub and ffdshow.
1.Setup ffdshow to work with Raw Video in its video control panel. Tick deinterlace and choose Yadif(or your favorite)
2.Setup Virtualdu(not much to do here)
3.Open VDub, go file-> capture
make sure your video source is displayed, after that: make sure the ffdshow video icon is in your system tray if it isnt then repeat step 1.
4.In the video menu select stretch to window.
5.In the capture menu select fullscreen.
Thats it, you can now play your ps2 games without lag, using a non bt878 capture source and have 50fps deinterlaced just like you would on an normal tv.
Programs i tried to make do this but would not: VLC, KMPlayer, Mplayer Classic, Mplayer Classic Home Cinema, DScaler(this supprised me as it worked well with my PCI bt878 Card but not my usb capture device(sleazy crap(easycap))
Oh i should also mention, use your sound cards line in for audio and unmute it in sndvol32 so you can hear it realtime without processing it.
This was the only method that worked for me with my usb capture device. If this method works for you please post below so others can see your success.