Wilshere was sidelined for almost 18 months with ankle and knee injuries before returning to action this season.
The 21-year-old continues to grow with every game and capped a man-of-the-match display to finally beat inspired Swansea keeper Michel Vorm with a 20-yard strike after 86 minutes to set up a trip to Brighton and keep alive hopes of Arsenal's first trophy since 2005.
"I didn't expect him to be this good at this stage," said Wenger.
"I always thought that if we could get Jack back to a reasonable level by January, we will have done well but he is ahead of what I could imagine.
"He is back to what he was before the injury, I think so, yes.
"A complete midfielder can defend and attack and Jack can also dribble and give a final ball so the closer players like him are to the goal the better it is for them.
"He has quality and enthusiasm - and a love for the game, which is the most important for me."
The Gunners were much improved from the lacklustre 2-0 Barclays Premier League defeat here by Manchester City on Sunday, and but for a combination of poor finishing and brilliant defending would have had the tie wrapped up well before Wilshere's fine late effort.