PSP. Great games, not only from first party but third party. Decent PS2 ports and was supported for quite a long time. The homebrew scene was amazing and it was my go-to for portables for ages... just for the emulation and utility it brought; in a pre smart phone era. Shame the Vita never lived up to its predecessor.
Top 5: GoW Chains of Olympus, GoW Ghost of Sparta, Loco Roco, P3P, Kingdom Hearts Birth by Sleep.