This is why I still consider AC1 the best in the series. Okay, it was a bit basic. Okay, it was a bit tedious to grind all those quests in order to unlock the next piece of story. But in the end, the focus was on what is supposed to BE the focus on a game series about assassins: assassinating people! And trying really, really hard to get away from the guards when your cover is blown, because they actually pose half a threat to you in individual numbers, and will most likely pound you into meatloaf if you decide to fight against three or more at once.
AC2 was also good, but that was mainly because they introduced a new collection of toys and ways to assassinate people. Unfortunately, it was also the game that introduced the limitless amount of gold that the game is way too generous with handing to the player. This wouldn't be so bad, if only there was something that might validate hauling around 100.000+ bucks. But there wasn't really, because everything that was worth buying only costed around 10.000 bucks, and everything else was just various things that increased the amount of money the game would throw your way every half-minute.
And it has, sadly, only been downhill from there...