I personally think Heaven is pretty great but it was done as a tribute to/written by Kieslowski (was going to be directed by him before he died) so it's like a cross between the two of them. I like The International; I think it's underrated and on a technical level, it's impeccably made as usual for him but it's crippled by some poor dialogue. Three is a pretty good but minor work for him. It's kind of him letting loose a bit again and just playing around - it's somewhere between the extremes of Run Lola Run and the methodical pacing of his other work. His two masterpieces though are Princess & the Warrior and Perfume as far as I'm concerned. Princess & the Warrior is closer to Heaven in tone so I wouldn't recommend that as much to you, but I think you should give Perfume a try, ilovemovies. It's a darkly gorgeous film that mixes all kinds of tones and somehow makes it all work - from dark comedy to romantic suspense/horror. I personally think the story feels surprisingly full and epic for a $60 million movie though with a very divisive ending (that I dug). I've also watched it something like 10+ times.
Also, here's the title image/font from Facebook: