Are you looking for something within easy walking distance? If so, it depends on where you're staying.

I'll presume you're staying on the Wisconsin Ave side of NIH, perhaps in the Holiday Inn, or whatever it is that the Governor's House is now. That's the one right next to NIH, on Wisconsin. Maybe it's a Clarion.

Louisiana Express is always a good choice, but it's more than a mile walk from NIH...and that's the Wisconsin Avenue side of NIH.

If you're staying at (the In-Towner oops, I guess it hasn't been called that in 25 years,) the American Inn, which is south a few blocks, you are less than a five minute walk from the Tastee.
The Pancake House, and La Madeleine are just another two or three minutes away. And Lousiana Express is about 5 minutes closer than it was.

If you're staying at the Pooks Hill Marriott, nothing is terribly close.

My choice is always the Tastee. Can't beat the price. And they move a lot of breakfast, so everything is fresh.