Pro Intense mercenaries mode
This mode give you the pure adrenaline you may be looking for. Score attack across most of the major stages in the game (plus a bonus Prison map). It relies on your combo counter of kills and knowing time placements and when to eliminate an enemy to best continue the combo.
Pro Meaningful cooperative gameplay
Where many games have you simply "play at the same time", RE5 requires you to coordinate your actions with your partner in order to succeed. Sometimes it's as simple as doing a "three hit melee partner combo", other times you have your partner's life in your hands as you have to keep a trap from springing, or providing cover fire from afar as they navigate an area.