Best Handheld Game System

[domflo]

I own GBA, DS, 3DS, PSP and PSVita.

Out of these systems, my favourite one would be the 3DS, since it's basically a DS stripped of it's GBA compatibilty. And since I currently consider 3DS's software library to be superior to GBA's (even though it is close), 3DS takes the cake over the DS.
That said, I love every handheld I owned so far. The GBA is an amazing system all on it's own (and actually my first console ever), only made better by that fact that it plays every Nintendo handheld game released before it.
The PSP probably offers the best value out of every system that you could buy at the moment. Not only is it itself fairly cheap (allthough I'd rather get a 3000 series used than buy the abomination that is the E1000 series), but the games are cheap, too. I have about 40 PSP games in my possession, and the most expensive game was Valkyria Chronicles 3 E2, which I had to import from Japan, and cost me 35€. The price of my PSP library averages out at 10€/game.
The Vita, although often overlooked, has taken a special place in my heart, too, and in some way manifests the gaming taste I have acquired over the years, which went from Pokémon and my favourite game of all time, Paper Mario 2, over the Fire Emblem series (my favourite series of all time) to a broader enjoyment of JRPGs and Japanese niche games in general. And there's plenty of them on the Vita, so I can't exactly complain.

And while I was writing the bit about the Vita, it came to me that 3DS does have region lock, so I might put the DS top, since, again the only difference in their game libraries is the difference between GBA/3DS games. It's really hard to name one of these systems your favourite when you think that they are all amazing. Although I can definitely say that I enjoy my Nintendo handhelds more than the Sony ones.