I like anime and manga because it has a different feel to it. It reflects a different culture and represents their ideas of humor, love, and adventure. When I first started watching them (started with Trigun) there were alien gestures, strange voice nuances, a very appealing character design standard, and humor that we do not use in America (as well as the lack of humor that we do). I loved the culture shock (I was shocked to see breasts in an anime clearly for kids when I saw Ranma 1/2... now I think nothing of it! Of course such acceptance in Japan has changed in recent years. ). Anime was also allowed to tread where American animations were not (this is certainly changing).
However, I do not necessarily feel there is more intelligence added to them. And not all animes are made equal. There are incredibly repetitious animes. And there are more copy-cat animes than I can count. Some genres are so cookie-cut it's kinda funny (there are way too many similar looking high school guys... of course they usually don't get the option of various hair styles or colors). Some are so empty that it pains me that they even animated it (possibly from a MUCH better manga). And some jokes are so recycled that you can see them coming before they happen!
Of course there are incredible gems amongst them. There are animes that have brought out more emotion in me than any American animation I've seen (think animations from Key). There are ones that make me laugh all the time (lots of them). There are ones where that awesome unlikely comeback makes you feel good to be watching it (first time I saw one was the Frieza battle in DBZ where you first see Super Sayian).
As for the fan-service that is ubiquitous throughout anime and not found in American animations... I don't mind that either
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