They were the same age.Without applying much nuance (quality of teammates, ice time, etc), Fantilli seems at least on par with Eichel regarding their draft seasons in the NCAA:
Eichel: 40GP, 71 points - 1.775 PPG
Fantilli: 36GP, 65 points - 1.805 PPG
although I believe Eichel was younger than Fantilli by about a year which is pretty significant.
Fantilli's numbers were impressive, I am more referring to their projection based on what I've seen in watching both of their games. I think Fantilli will be a very good player, but I don't see him being the dominant play driving player that Eichel has.