The single greatest album of 2003 is Apocalyptica's 'Reflections' album. Of course, this only applies if you like classical music as much as metal. These are the guys who made their names doing beautiful covers of Metallica songs via 4 cellos. They have matured into an unbelievable music making machine, and have other instruments involved now. Dave Lombardo is a guest drummer on a couple of songs. Unfortunately, it is not available in the US (due to contract issues, not protest) so I had to buy mine from Amazon.ca.
Another excellent metal/classical album is Malmsteen's 'Concerto Suite for Electric Guitar'.
These two albums are must haves for those with a taste for the genre.
PS: Dream Theater's latest album blows, so if you liked some of their older stuff, this will dissapoint.