You didn't buy a high-end PC or install PCSX2 to spend three hours playing the sub-par "Devil Within" minigame just to unlock one character. You installed it to experience the lightning-fast Mishima wavedashes, the brutal chain throws of King, and the perfect electric wind god fists of Kazuya.
Unlocking everything in Tekken 5 manually requires significant time investment. A 100% complete save file instantly grants you access to: Tekken 5 Pcsx2 Unlock All Characters Save File