That's true : Excel Saga, in essence, has no real plot. The whole take-over-the-world storyline is merely a skeleton to keep the body of work propped up, imo.
However, the main reason why this is considered extremely funny is because it pokes fun at many anime, many of which are mainstream/popular. It also makes satirical references to just about the entire anime industry.
The "plot" mentioned above is just there for cover-ups. But even so, the whole deal with parodies and satire are enough to make one keep watching, which is really what it's all about.
Anyway, um... OH!
For recomendations, I'll go with
Vision of Escaflowne and
Noir. They're both great anime with plenty of action and drama, but no real comedy, though.
Hm... oh, and Ranma 1/2, too, if you don't mind some
ecchi. It's really pretty funny, though. (Okay, and also because Ranma is so...
). =)