DelphiX may give you lower results than theoretically possible if WaitVSync is set to true (which is a parameter of the Flip method). So you may get a frame rate around 60 FPS even if your engine is actually capable of much higher frame rates. This doesn't mean you should disable VSyncing, it just means that your game may run at the same framerate on slower machines.

There are of course ways to optimize the speed of your game:
1) Avoid using alpha blending as this will significantly slow down blitting.

2) Make sure you only draw what's actually visible (if you have sprites, check their X and Y coordinates to see if they're currently visible on the screen)

3) Draw things that don't get updated a lot on a separate surface and then just blit that onto your backbuffer.

Hope that helped.