Maybe it is also the sense of vulnerability and realism? I mean, in SC (or thief etc), you're pretty vulnerable, same with the classic Hitman games. In MGS I always felt like 'they are trapped in the room with me' if you catch my feeling. Hard to describe.
SC also felt the most 'real', as-in, I could see these missions really happening (outside of some bonkers setpieces).
I think that's it, really. SC definitely feels
more like a stereotypical stealth game than MGS in terms of its presentation, lighting, sound effects, etc... And almost all modern first-person stealth games utilize a similar visual language and sense of realism, which helps to codify these things even further.
But, as we alluded to earlier, mechanics should come first and gamefeel alone should not define genres. And that's why I wanted to underline the notion that all mainline MGS games are fully-fleshed out stealth games through-and-through in my book, despite them not necessarily looking and sounding like it at first glance.
MGS2 started out really stealthily too though imo, but later-on felt less so. The boat was my favourite part as a result.
I think this is an excellent example of what I mean. The Tanker section is my favorite as well, but does that make the Plant section any less stealthy? I don't think it does. Every room in the Plant has its own set of guards whose pathfinding routine is carefully designed around an optimal path for the player to discover and take advantage of. The objective is almost always the same: to get through the area as efficiently and silently as possible, and there are always penalties for being discovered. If that's not stealth, what is it?
I always liked ranks, but also disliked them in Stealth. [...] It feels like it takes away more than promotes creativity.
Fair enough, although I would point out that creativity may not always be the best metric of this sort of thing? Reminds me a bit of the NG/Efficiency vs. DMC/Creativity debate, really. Sure, you will probably not be able to make liberal use of your entire bag of tricks when going for the higher ranks, but there's value to be found in efficient play as well.
And it should also be said that MGS handles the intricacies of its ranking system a lot better than SC from what I can recall. Japanese arcade design sensibilities and all that.
Let me put it this way. Hitman has very little in common with Splinter Cell in terms of either mechanics or presentation as well. Does it mean its own special brand of "Social Stealth" is enough to shove it out of the genre bracket?
Let me put this another way. If every racing game in existence was a GT-style simulator with the exception of F-Zero, would the latter be any less of a racing game simply because it looked and felt so different from the rest?
To make a long story short, looks are not everything is my point.
For the record, I've played through SC 1, PT, CT, DA and Conviction once. Loved them all except for Conviction, which I found very meh. I've been thinking of replaying CT recently and perhaps trying out BL for the first time. So I do have some experience with the series, albeit nowhere near as much as I do with MGS.
PS: MGS2's VR Missions are a fantastic addition to the main game, and many of them force the player to master the core stealth toolkit. Well worth revisiting for those interested in reexamining the game's mechanical fundamentals.