They are used to Apple products iPad/Pod/Phone and I like them because there's hundreds of free games, but they've smashed the iPod screen and also cracked my iPad screen, so I am considering something more robust.
I like the Meep as it has a rubber grip surround, but their website is slow and I don't have the patience. But I know nothing else about the product.
My 7 year old DD enjoyed what I think may be a handheld Nintendo at the Butlins games portal (transparent blue case), but again I know zero about any of these products.
Obviously price is a factor especially the ones that require separate games cartridges.
And before anyone asks, yes they've tried my old Gameboy and got bored of Tetris and Mario within half an hour 