Love Messi, but it's a clear exaggeration. Player like him come along every 20 years, two previous ones (Maradona and Ronaldo) were equally or more talented, just less protected on and off the pitch. I bet we'll see another superstar emerging in 2020's.
If he comes to the Etihad though, he'll be head and shoulders better that any City player, simply because this team isn't that special individually, contrary to the media narrative ('City have bought all the best ones)'. The only current City player who'd get into that legendary Barca side on a regular basis is probably KdB, and he wouldn't be replacing Xavi/Iniesta, that's for sure.
Sometimes I feel Pep isn't getting enough credit for his work, for the way he makes very good, but not exceptional players to perform as a superstar team. Maybe Messi rocking up at Manchester and demonstrating the gap in quality would make people understand it a bit better