I wouldn't go into "Galactico" signings. I'll classify signings as big signings or not.
If I remember correctly, we made many signings during the first few years of the Sir Alex era. The likes of Bruce, Pallister, Ince, McClair, Parker, Kanchelskis etc., were some of the signings I remember. Then, we made probably a big-ish signing in Schmeichel, seeing as we bought him after his Euro 1992 heroics. Cantona was the same: not really big, but something of note. I think our first big signing was Roy Keane. He would be equivalent to us getting M'Vila, for example. Next came Andy Cole, who wasn't a big signing considering we were linked with Shearer. Then there's Ole Solskjaer, who was in no way a big signing. Same with Yorke. The Poborsky signing was a big signing, considering he impressed at Euro 1996. Stam was a big-ish signing as well, just something of note, nothing big. van Nistelrooy is equivalent to us getting the Cavani of last season: a really promising player who has world class potential. Then Ferdinand was a big signing. Veron was an obvious world class signing. The Rooney signing was another big one, equivalent to us getting Hazard or Muniain. C. Ronaldo was not as big a signing as Rooney, but was very notable, like us signing Ramsey or Oxlade-Chamberlain. Berbatov was a big signing as well. Don't forget, we also had signings like Nani and Anderson who were promising players for the near future at that time.
Going back to what Matt said about us attracting more young players, I think the reason we went for those transfers so much at that time was because our academy was not producing much talent back then. The best that was coming out at that time was probably Richardson and Eagles. And we only had O'Shea and Fletcher make it at that time, too, which wasn't much. That's why we went for such players, as we didn't have much good talent for the future. Now, we have Cleverley, Welbeck, Pogba, Petrucci, Will Keane, Fryers, etc., looking promising.
That's my view, though. I'd still think we can get some big signings if we wanted. However, Sir Alex has learned his lesson about buying established players who aren't suited for his system, as he already has had failures with Veron and Berbatov, both of who didn't fit into this system, and so he is more careful about getting established players.