MGS2 and Prime lack the more modern visual techniques and features which Splinter Cell helped pioneer but, ultimately, those games stand the test of time in a way that SC does not. I would argue that Rogue Leader, released alongside the Gamecube in 2001, is more impressive than Splinter Cell on all fronts.
That... is true, I would agree. SC1 was a very bleeding edge game focused on a very specific tech ambition that is kind of ugly if you take a step back. I would say, however, that Chaos Theory and Double Agent on Xbox and even PS2 hold up very well today. (Chaos Theory on PC is even better.) I recently replayed DA on PS2, and thought it was a visually beautiful game at times.
But that's a separate issue because they're 2005/2006 games. They're the product of several years of technological refinement. And they are 30fps.
The frame-rate is 60 frames per second, the art is perfectly designed around the limitations of the hardware and they ooze polish. They simply look nicer in motion. Splinter Cell feels like a game that made a lot of sacrifices to include new visual features.
The discussion around that era is interesting then as I feel the best looking games are more balanced titles which offer the perfect blend of visual complexity and performance.
I feel this is a very interesting point. Console games in the 6th generation that targeted 60fps are very interesting. Beyond Good & Evil, for example, was a very pretty game with remarkably clever reflective water that targeted 60fps. All the TimeSplitters games targeted 60fps. (It was apparently a kneejerk response to disagreements during Perfect Dark's development.) I don't know its actual framerate, but I know 007: Nightfire targets 60fps, and it is a very nice looking game. And of course everyone knows about Rogue Squadron and Metroid Prime. It would actually be nice to know how many 6th generation games were 60fps or at least tried to be 60fps. Because almost nobody records those old consoles at 60fps, it's not easy to check without grabbing some real hardware and recording some video.
Games running at 60fps didn't get the appreciation it deserved back in the day. Performance matters. And it drives developers to developer better tech. Not just fancier tech that's fancy for the sake of being fancy. Fundamentally better tech.
What you're basically talking about is the move to programmable shaders which became common on the Xbox but I feel like many of the games which leaned heavily on these techniques have aged poorly. The best looking games on Xbox tend to dial back these types of techniques, I think. Ninja Gaiden lacks many of the features you see in Splinter Cell but is the more impressive game to behold.
I'm of two minds about that. I think games like Chaos Theory hold up beautifully, as I said. However, I think it's true that many Xbox and overambitious PS2 games jumped the gun visually and tried to cram in visual effects at the cost of overall visual cohesion. Looking at the big picture, yea, many of those shader-heavy games aged poorly because they were so tech focused. (Matrix: Path of Neo comes to mind, oddly.) And this wasn't actually unique to those platforms. One of the most glaring examples of this problem is Perfect Dark: Zero for Xbox 360. Perfect Dark: Zero is kinda like Splinter Cell 1. It's a crazy ambitious game from a tech perspective. But it runs like a dog and its so incredibly ugly. (Not to mention the gameplay is such a step back from its predecessor.)
I look at these two screenshots. They're both Xbox 360 games. One from PD: Zero from 2005. One from PD XBLA from 2010. The 2005 game is so far ahead of the 2010 game when it comes to graphical tech. But the 2010 game runs at 60fps, and holds up very well visually all these years later. Nice texture work and a rather clever "fake" dynamic lighting model that allows for lights to be shot out.