AC Milan was in a very poor state when Berlusconi bought it, but only Juventus had more Serie A titles than them, historically they were battling with Inter to be the second biggest club in Italy, but mismanagement did them dirty and almost bankrupted them.
City was nowhere near to be considered big in England until the takeover happened, to the point that many people outside the british isles only knew about their existence when Abu Dhabi bought them, before that Manchester was associated exclusively with United.
Berlusconi certainly saved Milan from bankruptcy, but he was buying a big club that was considered the second biggest in Italy just behind Juventus. City was a minuscule club that players outside of the british isles didn't know.