You're talking to the Cartoon network junkie hear (and I can prove it, too, just check my spelling and grammer)
Yu-Gi-Oh- Good show. Interesting plot lines, all though it get repeatative after a while. And, it teaches kids lame things like "the power of friendship"
Pokemon- Personally, not a big fan, but I can see hwere kids like it. It has the cartoony fun, with a sports setting, and it teaches kids the same lame things like "the power of friendship."
X-Men- I assume you mean the new X-Men Evolution, right? It is an ok show. Kind of like X-men meets a WB teen drama kind of thing. But instead of the kids dealing with issues like teen sex and drug aduse, as those dramas likes to do, it deals with mutant powers and obeying your elders and stuff. Personally, I'd let my kids watch it LONG before I let them tune into Dawson's Creek or 90210 or One Tree Hill, or any of the other countless teen dramas.
Power Rangers- I was duped into watching an episode of that last night. It is the same as it was when I was in first grade (back when they had the first 5, man am I getting old). I remimber playing the Red ranger on the playground. The concrete play ground, with sharp metal all around... Anyways, the fights scences arn't Jet Li qualities. In fact, they arn't even as good as the first 5 guys! And they still have the disrespectful attitued, but without there mini-PSA about self esteem or friendship after the show. If anything, the one single Girl ranger in her body suit when she goes surfing (yes, surfing) might not be the kind of thing you wnat your kid to see right now. I mean, she is super-fine and all, but still...
In short, they are good shows, I dont see a problem with them that will warp your kids mind and turn them into Pinko's or gang members or... Charismatics!

Well, now I'm going to go into my room and hang my head in shame, over the fact I, and 19 year old, watch 2 of the 4 shows you listed...

Thanks for deflating my ego.

COme again
