Good Czech food can actually be found in Prague. Which is not to say it's light, but it's as flavorful as it is heavy, while the bad stuff is even heavier plus tasteless.
I live by the Andel metro stop on the B line in Smichov, which is bustling but not touristy, so I know the restaurants nearby best. If you don't mind a ~10 min metro ride, here are three places with excellent Czech food:
Potrefina Husa - I think this is actually a chain with a few locations, but I know the one by Andel. Excellent goulash, served in a bread bowl. Other food equally good from what I've had, which is only a few dishes. On the same street as the Andel metro exit, English menu ("ongleetzkeh menny," FYI) available.
Na Verandach - this is the Staropramen brewery restaurant, across the street from the Andel metro exit. Again, excellent goulash (served more traditionally, on plate with dumplings) and other Czech food. Never an available seat on Friday nights, though, so be forewarned. English menu available.
Na Vaclavce - excellent and at times adventurous Czech cooking, a few excellent veggie dishes, huge, delicious salads. Traditional Czech holiday foods around the holidays. A restaurant for locals, so high quality and low prices. Monthly Thursday theme nights, with Balkan food, Mexican food, etc. The occasional Doors cover band(?!). Cons: not near metro, no English menu, Doors cover band when you just want dinner. If you might want to seek it out, here's a link to the website, which features a map: http://www.navaclavce.cz/index.php.
Also, as has been said, Prague for some reason has excellent pastas and pizza. My favorite pizza place is Kmotra.