The fact that you mentioned there was no sound makes me believe that the actual game may not be coming on at all. The marquee will because it's just a light fixture like any other light in your house, the monitor effect you're seeing leads me to believe the monitor is "functioning" but without a video signal. Check out the power supply and the game pcb for loose connections etc. You should be able to at least play the game "blind" (no video on the monitor) if the game itself were working correctly. Don't count out the monitor until you can actually hear a game being played.
Is the regular NFL Blitz a hardrive game? (I think 99 and up is, but not sure on the older one) If it does have one, is the hardrive spinning up and functioning at all?