3. Spider-Man 2
A huge, vibrant, living world. Tons of side quests. Ambient events. Upgrades. An unparalleled traversal system. When it released, this tie-in to the movie blew absolutely everyone away, and for good reason. Nothing had come close to matching this kind of scope before, and being able to run between cars on the streets of Manhattan, bound off a lamppost, and run all the way up the tallest building before launching off and swinging between the skyscrapers was an endlessly entertaining activity. In a truly fantastic touch, the webs had to attach to actual objects and physics respond accurately as such: shoot a line at the corner of that building and swing around the building, or attach to that helicopter and hitch a ride around the city. Hidden around the world, and granted through combat, were additional offensive moves, abilities, and other upgrades. This game was awesome, and set the precedent for superhero games.