You can go to the National association of epilepsy center website, check which epilepsy center is (Level 4) which means they do complex epilepsy surgeries with invasive EEG monitoring. (Don't go for level 3 centers).
Your ideal epilepsy fellowship should train you on surface EEG interpretation, epilepsy evaluation, and epilepsy pre-surgical evaluation.
It is very desirable to have exposure to invasive EEG monitoring, especially with stereo EEG, which is a new growing field (which requires utilizing a robot that costs a million dollar, and not all centers have it).
Do your own search about the faculty of each program. In general, good epilepsy program should have adult and pediatric epilepsy faculty, adult and pediatric epilepsy neurosurgery faculty, and high numbers of EMU beds and a robot for stereo EEG.
I agree with the aforementioned post (Cleveland/Mayo/Stanford are great). In Chicago also Northwestern is top tier. UPMC in Pittsburgh, and others.