Yes! Finally a game that I can take with me to the next day and write a second hint for. The two guesses so far, Call of Duty: World at War and Medal of Honour (I assume Allied Assault?) were both wrong, but close. The former mores than the latter, or was it? Anyway, forget the whole sentence, you haven't read this, time for the actual hint, and one for a new game;
#24: This game features an awesome campaign following three characters from three different viewpoints, and with the expansion ends with an iconic image of carrying a flag onto a rooftop.
Hint 2: There's other levels that are reminiscent of real-life locations or events. One level, taking place in a village in France, looks pretty much exactly the same as it did on an episode about the same events of an otherwise unrelated HBO miniseries. This level is coincidentally also one of the most popular multiplayer maps. Guessed by coolbeans - Call of Duty
#23: Even though you can do each of the levels in any order, it's usually a good idea to one in particular first, because the weapon upgrade you get from that boss is good against pretty much anything. Guessed by The_Liquid_Laser - Mega Man 2