Stealth games are weird. Splinter Cell: Conviction is the most fun I've had with a stealth game, take that how you will (I really liked conviction). I also played both Crysis games like stealth games. I had a good time but often found myself avoiding most large encounters with enemies and felt like I was doing the game wrong for most of it (I was missing most enemy encounters). But surely invisibility was included in both games because stealth was supposed to be a core gameplay mechanic. What I'm getting at is that for a lot of people they don't feel like they are playing stealth games right and that's what people find off putting.