Since getting into mecha anime, sparked by Gundam 00 when it came out, I've managed to amble my way through a (very) select few similar series. Having seen some older offerings (Gundam SEED and SEED Destiny) and some more recent beasts (Asura Cryin') I can say that the appeal of 60' robots blowing stuff up is, well, appealing.
On this basis I decided to watch Evangelion, often considered a classic for its directing, pace, action and philosophical lessons: I found it to be a good watch if not unfulfilling. The ending is horrible, well, if you can call it an ending. In my opinion, whilst I salute the creator for making a series that does raise some interesting existential questions, I'd prefer a (relatively) clear cut answer!
Saying that, ending aside, the series as a whole is fantastic. The characters are demonstrated to have depth and their relationships with each other adequately reflect their mental states. The pace of the series is good, with the plot development coming along at a reasonable pace. The final 6 or 7 episodes are rather fast and are very difficult to follow, End of Evangelion fortunately provides a more straightforward, albeit grandiose, ending which should be watched in addition to the rest of the series.
My other main criticism, aside from the rapid pace of the ending, is the angels. At first they appear as monstrous enemies, with the Evas as mankind's only hope against their power. This feeling rapidly ends after the death of the first angel. The introduction of new angels rapidly becomes a monster-of-the-week style event, often appearing at the predictably worst moment for the characters.
These criticisms aside, I can't say the series didn't entertain me or leave me wanting to watch it through to completion. Overall, it's a damn good series with some fine directing and good artwork.