Just like any game, really. Most recent example is when I play BC2, and I play by my self and always die by lucky people, 40mm grenade spam, people using vehicles all the time, brain dead team mates not doing the simple things for the team and people using broken weapons.
Then there's times (usually) where I'm with bros, in a squad, always MVP, always getting amazing kills and doing awesome team work and always winning, and I feel as if the game is the best I've ever played. The gameplay and graphics, and especially the sound are all nice, and it all gels in together and I have a wargasm!