I know there are some cool DS and GBA games only in Japan...but I've heard before that it is just as cheap to import through Play-Asia or such than it is to pick up in person....
Is this true? Are there any must have games I should have him grab while he is there?
For the most part, it's true. Japanese gamers pay 20-40% more on average for their games than we do in America. However, the used game industry is huge in Japan and you can sometimes get a good deal on discount games but finding a good deal in terms of price and being in stock can be time consuming.
It's also hard to recommend games unless we know what you like.
As for Bit Generations, it'll probably be $20 a piece when it's out here. I think this series is actually cheaper in Japan, but I'm not sure.
I'm tempted to have him grab an Ice Blue DS Lite or white PSP.
This is one case that is actually the reverse of the above since online import retailers have to pay hefty overseas shipping fees for systems. If you have an interest in any Japanese controllers or accessories, it's also cheaper to get them this way.
However, it should be noted that neither Nintendo's nor Sony's America branch will honor warranties from their Japanese counterpart. So if something is wrong with it, you'll have to ship it back to Japan to get it fixed (which is expensive as previously noted and can be difficult due to language issues). Additionally, Japanese consumers don't enjoy dead pixel policies to the extent we do here. Many retailers will not allow you to return a system if there are a few dead pixels in it.
Bear in mind I don't care for Anime and can't read a lick of Japanese....
A lot of the popular Japanese titles don't require you to read, such as music games like Ouendan or Daigasso Band Bros. But again, we need to know what genres you're interested in. And most anime games aren't very good anyway, so you aren't missing out. Although, the GBA boxing game for Hajime no Ippo is really quite good.
I'm a big DC Superheroes fan too....
There really isn't much DC stuff going on over there, the American comics market is very niche. Unless you're just saying this to let us know, in which case, Marvel for life but Batman's the exception.