Actually, the best of Pantera can be found at Metal Sludge's tribute to all things Phil Anselmo's hairpsray.
As you can clearly see, at their inception Pantera had an overly glam image. This image, like a brainslug from outer space, had complete control over its hosts. Their glam image forced them to dress like She-Ra. Fortunately, bouts of Jack Daniels-fuelled fueds with fellow Texans considerably toughened their skins and they kicked out the metallic jams short before long.
Dimebag Darrell (R.I.P) became the patron saint of nineties shredding with his manic chromatic runs, his Eddie van Halen-style riffs and his Ace Frehley inspired stage moves. Not to mention his trademarks - the Dean guitar and the She-Ra purple beard.
Rumour has it that old Phil indulged too much in drugs and became somewhat difficult to work with. This is why the later Pantera albums fell a little short of the glory. I gave Damageplan a few spins, it was not too bad at all. Actually, I really liked their singer and it sounded like Dimebag got a bit of his old magic back.
The Cowboys from Hell is a classic album, with more 80s style singing than the later growls Phil Anselmo tried. I still think it is their most solid album, even though it does not contain their most well-known tracks.
In view of this, your best bet would probably be to get the greatest hits. All their party anthems are here on one disk, back to back.