I've never played a Pokemon game, but I've read about them and have a pretty good idea of the content and gameplay. I've also played plenty of games that involve summoning monsters, casting spells, etc.
Pokemon is fantasy and I see nothing inherently harmful to it, aside from it being potentially addictive. If you're going to make it off-limits, you might as well do the same with Tolkien or even C.S. Lewis' Chronicles of Narnia. I definitely don't believe the game is SATANIC. However, I can understand why people might be concerned, I'll acknowledge that there's some legitimate basis - albeit small - for that concern.
An example that came to my mind was something that's better known for controversy -and understandably so -than Pokemon, Dungeons and Dragons. I used to be into table-top role-playing games, including D&D and similar RPG's. The other guys in the group were devout Christians and I was at that point at least loosely religious, and none of us had a problem with it. None of us ever had the urge to practice magic or summon monsters anymore than we ran around lopping peoples' heads off with broadswords. We understood that it was all fantasy and just a game.
Unfortunately, not everyone is like that. While it's unknown how much of a problem it's actually been, where there's that much smoke, there's at least some fire. When people who have difficulty separating fantasy from reality get into something like that, there's potential for harm. I certainly don't think we should ban D&D because of this anymore than I think we should ban cars because some people are too incompetent to drive them. But I think we have to recognize that potential for trouble exists.
If I were parent, as long as my child clearly understood that the game was fantasy, or "just pretend," or whatever, I'd be okay with letting them play Pokemon.