Would you even count van Persie in that bracket? Played well for a season and won them the title, but then reverted to his usual crocked self. 26 league goals in his first season, then only 22 in the following two combined.
There's a reasonable argument that the last great transfer window was the 05/06 window when they brought in Vidic, Evra, van der Sar and Park. Since then, you could only point to Carrick (06/07), De Gea (11/12) and Shaw (14/15) as players that have had a long-term role in the first team at a fairly high level.