The next variation is even worse for Black.
4.Ng5 d5 5.exd5 Nxd5 Two Knights' Defense

I would never touch that variation with 5...Nxd5. For one thing you will often face the knight sac variation, and black cannot gain an advantage without perfect play until move 20! Even in correspondence the variation would be difficult. Not to mention the Lolli Attack which virtually guarantees white a significant advantage.
This position was covered in a recent Chess Life issue where Jon Edwards attempted to resurrect the Fried Liver (Jon Edwards, July 2009, "Re-Fried Liver," Chess Life, 32-34). However, he missed a critical improvement for White in the Lolli Variation.