The Fountain, definitely. You can often find it in "Oscar snubs" lists. Even with his later work (which I loved), I think it was his best acting.

A lot of his acting credits are definitely recommended. Wow!

I would go for Prisoners and The Prestige.
He is also amazing in The Fountain.

I'm the best at what I do, and what I do best isn't very nice.
I'm the Wolverine.

That's a good start!
Hugh is a very versatile actor and his film portfolio has quite a few gems.
*Musicals if you can find a copy of OKLAHOMA! (or just watch the upload on YouTube), he is a very charismatic Curly, complementing his singing with his acting and dancing skillsthis is a filmed stage performance ( Hugh is also active in the theatre).
*Drama you may want to watch a drama-thriller by upcoming director Denis Villeneuve called PRISONERS, a period piece drama thriller directed by Chris Nolan called THE PRESTIGE, an epic saga of his home country directed by Baz Luhrmann called AUSTRALIA, a Darren Aronofsky personal masterpiece called THE FOUNTAIN ( which has metaphysical elements).
*Comedy/Family Friendly Woody Allen dark comedy called SCOOP, a PeterPan prequel directed by Joe Wright called PAN, a recent release about a real-life Olympic skier called EDDIE THE EAGLE, and a romantic comedy called KATE ANd LEOPOLD ( this is a favorite with the ladies!).
*Action Of course the XMEN movie franchise which he headlines as WOLVERINE ( check out XMEN, XMEN United, XMEN Days of Future Past, and THE WOLVERINE at the very least). Some find XMEN ORIGINS : WOLVERINE divisive as to its execution, but I do like the drama presented of his origin and Hugh's acting performance as well.