Metroid Prime and Resident Evil 4. Both fantastic evolutions in their respective franchises.
Metroid Prime managed to not only recreate the Metroid feel in 3D but using a first person perspective. The exploration is engrossing, the boss fights are spectacular and it's a pleasure to hunt for new abilities and power ups.
Resident Evil 4 updated a series that was getting stale, just by the intro you knew you were in for quite a ride. Having the villagers hunting you throughout the streets, up the stairs and the rooftops was exhilarating. The game is wonderfully paced, each location not overstaying its welcome, each new area bringing new challenges, the story was camp but enjoyable and Leon kicks ass.
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