Because Evangelion has a terrible, terrible ending. End of Evangelion was a better ending, but was still pretty out-there. I'd say it's worth one watch, but the ending just spoiled it all. I completely expect that the new Evangelion movies will have an equally screwed up ending as well.
I really enjoyed Eureka Seven, though Renton can be a bit whiny, though not to the same extent as Shinji and the plot can be a bit confusing at points, but it generally all makes sense by the end. Just don't near the movie. That is awful. Very awful.