If all games worked flawlessly in the store, and all games have wavy lines at home, I'd bet safe money that your TV doesn't like the NES.
Cleaning the games doesn't typically help with video output issues unless you're talking about graphical "glitches" that could be the product of the 72 pin connection not completing properly to transmit data. But "wavy lines" sounds like a video output issue.
Again, try a different TV and see what happens.







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