The Reds paid Sunderland £16m for the midfielder in 2011, with the former Black Cats youngster struggling to live up to the sum since his arrival at Anfield.
However, Aldridge believes that the England Under-21 captain is finally beginning to show why the club spent so much on the player.
"People couldn't see why the club had spent so much money on him; they didn't see what he brought to the team and they questioned the logic of his signing," Aldridge wrote in his column in the Liverpool Echo.
"He had his critics last season – and I was among them, by the way. They aren't questioning him now. He's improving every time he pulls on a red shirt, and I do think he's becoming a very important player for this team.
"Henderson looks like a player who loves playing football, loves playing for Liverpool."
Henderson equalised for Brendan Rodgers's side in their 2-1 win against Aston Villa on Sunday.