What is a good TOEFL score or a good GRE score that a typical U.S University expects?

That depends. Some Universities look at only V+Q, others look at Q+AW and some look at V+Q+AW. Then of course, the perception of what is considered an acceptable score varies from University to University depending on its competitiveness. Even within the University, various departments may set their own standards. Typically the CS and EE departments are very competitive and may set higher standards for admission and f-support compared with the other departments. But, in general, for a 2nd tier (mid-level) Universities, a V+Q+AW of 1100+,Aw=3.5 is considered acceptable, 1200+with 4.5 in Analytical Writing section is considered very good and a score of 1400+ with5.0 means that you stand an excellent chance for an assistantship in the first semester itself, if you have 80% in your academics. Low GRE scores can be compensated to some extent by excellent academic records, and vice versa.