Crysis 2, on the other hand, utilizes many pre-rendered videos (that are very low quaity / resolution). The original game rendered every cutscene in-game as far as I know and this essentially made the game future-proof (cutscenes will run at any resolution, framerate and aspect ratio you throw at it). In C2, however, there are many scripted and unskippable set-pieces, slow-walking story sections and QTE events. The player had control pretty much all the time expect in cutscenes (that could be skipped). The first Crysis was really gameplay-driven (like Half-Life and Dead Space). In Crysis 2, there's almost no destruction. It didn't just add to the immersion but it also made possible for the player to express himself/herself in really creative ways (make a tree fall on a soldier, blow up a house with soldiers inside of it etc.). The environmental detruction and general environmental interaction was a huge part of the original game. Yet, the sequel switched this too to more humanlike "robot-aliens" that are just as generic as they possibly can be. The alien design in the original Crysis is one of a kind, it's extremely unique and memorable. Crysis 2 compared to it was just a corridor shooter with very little options available to the player. Crysis had a wide-linear level design for the most part which was amazing because the story and gameplay managed to stay tight and focused while at the same time there was enough room for the player to express himself/herself (in how he/she wants to approach enemies, what objectives he/she wants to do etc.). This way replaced with New York in the second game, which is pretty much the most boring video game environment you can think of and one we have already seen countless times in many other games.
Aside from Nomad, what's an iconic element of Crysis too is the lush, big tropical jungle. Yet Nomad was killed abruptly off-screen and got replaced with generic random soldier guy #23. Nomad is just as iconic to Crysis as Master Chief is to Halo or Gordon Freeman to Half-Life. It managed to completely strip away the identity, the originality and magic of the original, and replaced them with mediocrity at best. But for those who do not want to read this much, here's the TL DR: Crysis 2 to Crysis feels like what the prequel trilogy were to the original Star Wars movies. I think the best and most simple way to explain why it was such a let down is by comparing it to the original.