If I want to look at something pretty, the internet has plenty of amazing things. No matter how nice the jungle, I've seen landscapes that it just cannot touch.
When Crysis came out it was wholly new. You could dick around, and do whatever you wanted. Did you want to stealth in, have a silent genocide, then disappear into the night? Did you want to level the entire area, leaving only a smoking crater in its place? We got the chance to do either option, and everything in between. No two instances were completely the same.
It was pretty, but it was also a decent game. Story was...somewhat lacking would be a charitable way to put it. At the same time, the Ceph were a decently mysterious and fun enemy.
That's why people want something more from Crysis. People were pissed with Crysis 2, but it seems like Crytek only listened to their words, rather than the sentiment. People immediately railed against the visuals. Crytek answered by saying it was PC first. People complained about the multiplayer. Crytek attempts to make that more compelling. What people didn't articulate well is that a tacked on single player game was unacceptable. We expect Crytek to know that, but rarely articulate the sentiment to them.
Is it unreasonable to ask that Crytek have the same vision that created Crysis, but put more polish into it (ala Crysis 2)? I think it's reasonable. Crysis, with more polish, better design, and some streamlining is what people want. If Crytek could deliver that then people might be satisfied. As it stands, it seems like Crysis 3 is more appropriately 2.5. It continues an unfulfilling story, that might be passable if it were taped to the end of 2. That kind of disappointment is what people want to avoid.