I've put together a list of players who had a torn ACL, with their age when the injury happened indicated:
Recovered nicely and went on to re-find his form or become a quality player
Evgeni Malkin (Age 24)
Niklas Kronwall (Age 24)
Justin Williams (Tore his left ACL twice – age 21 and age 26)
Johan Franzen (Age 29)
James Wisniewski (Tore his right ACL three times – age 18, age 23, age 24)
Josh Gorges (Age 18 – played with it for 8 years)
Jared Cowen (Age 18)
François Beauchemin (Age 28)
Milan Michalek (tore right ACL at age 18 and tore his left ACL at age 25)
Erik Johnson (Age 20 – although you could argue he was better as a rookie than now)
Josh Harding (Age 26)
Dany Heatley (Age 22)
Marian Hossa (Age 19)
Todd Bertuzzi (Age 24)
Jeremy Roenick (Age 25)
Michal Handzus (Age 29 - had 2 more good years)
Daniel Alfredsson (Age 35 – not 100% sure this was a total tear though)
Pavel Bure (Age 24)
Andrew Brunette (Age 35 – 2 more solid years after)
Decline after the injury but still solid or good
Saku Koivu (Age 22 - was leading league in scoring, still a real good player after)
Michael Peca (Age 28)
Major decline after the injury
Alex Kovalev (Age 37 - was close to done anyway)
Marco Sturm (Age 31 – was already on the decline when he suffered it)
Brenden Morrow (Age 29)
Marek Svatos (Age 25 - already on the decline when he suffered it)
Derian Hatcher (Age 31 – the new NHL basically killed his career)
Scottie Upshall (Age 26 - was having nice 2009-10 before injury, not the same since)
Brendan Morrison (Age 32 - was already on the decline)
To be determined
Andrei Markov (Age 31 - unique case with 2 torn ACLs in a 6 month span, was starting to look his old self as the season ended)
Hossa, Michalek, Cowen, Wisniewski and Gorges were considered prospects when they were injured.
In short, the success ratio for players 25 and under coming back from a torn ACL and being a quality player again is EXTREMELY good.