To me, the logical explanation of "Next-gen" has changed over time. Let's break it down:
Nintendo Entertainment System - Incredible, timeless games which set the gameplay-oriented and graphical groundstones for the next generation. The graphics are dated; It's the NES.
Super Nintendo Entertainment System and Sega Genesis - The industry was just starting to hit its stride, and not only were 3D technologies impossible, but the public simply wouldn't have been ready for them. The SNES refined the brilliance of the NES' visuals to a then-staggering level of detail and color. This was its purpose, and the same goes for the Genesis.
Nintendo 64 and Sony Playstation - Now, this was a real revolution. Think back to when you first played Super Mario 64; did it astonish you? It must have. The first truly mesmerizing, fully-expansive 3D world had been realized, and in my opinion, was perfected, and perhaps never done so again. Think about ALL the things that could have gone wrong with the first 3D Mario outing: The controls could have been unresponsive, the animation could have grossly inhibited the free-roaming gameplay, and the game, which no one had ever seen anything like before, could have been, simply, a wasted effort. It was not. Nintendo re-invented the videogame, and they did so to a level of flawlessness which was not met by any of the Playstation games, or most - if not all - of the following generation's titles.
Gamecube, Playstation 2, XBox - These were meant to bring gaming to a new, advanced level of what it had become the previous generation. They astonished all who played them, as they were SUCH a dramatic leap in visual and control-oriented complexity. The games were good, and they were what they were meant to be.
But now things change.
Look at the XBox 360 compared to the XBox. Some games are drastic graphical improvements, but not primarily in the way that you might think. Look at Call of Duty 2; it's wonderous, and, more than anything, engrossing. It pulls you in to a full world, with things going on every way you turn, all in real-time. That's engrossing. A "Weaker" version of the game is available on the other systems, as well, and therein lies my point.
Every game system until now has given us something new, or, at least, an immeasurable improvement over a previously designed concept. But now we're getting into the new days, and you've gotta wonder if some better textures, lighting and effects are truly revolutionizing the games we play. Are they worth the extra dough? More than that, look at the controller; there is essentially one new button from the previous XBox controller, and it's not even used in actual gameplay. Is it worth 50 dollars for a wireless version of something we may already have 4 of, and must now throw away? Moving away from that, at what cost is this new level of engrossment coming? In NBA Live 2K5, for the PS2 and XBOX, there were several modes, levels, and options, including the main season mode. For NBA Live 2K6 on XBox 360, they took out almost every single mode - including Season - in favor of minorly improved graphics, until you get really, really close - usually during non-gameplay gutscenes, when you see "Amazing" sweat pouring from the hair of the players. That would be great, if it were visible when actually playing the game, and if it didn't come at the cost of 90% of the game's depth.
Amped 3 is a better GAME than Amped 1 and 2, but looks virtually identical.
Tony Hawk's American Wasteland.
Moving to the PS3, I have to say, it looks phenomenal. The videos I've seen of it have truly blown me away, and if they're not enhanced or forged (as has been suggested), then they shouldn't be able to keep the systems on the racks... if they were marketable towards households, as Sony themselves have said they are not. Apparently, unless they can find dramatically cheaper parts, they will not be able to market the PS3 for less than 700-800 dollars. And that's wrong. Also, the controller, while "Not a part of the Dual Shock line," as Sony has stated, is, in essence, a cooler, funkier Dual Shock 2, with almost identical button mapping.
Then there's the Revolution.
The Revolution may change gaming as we know it, as we have truly never seen nor invisioned anything of the sort. Not only that, but even with the "Weak specs" supposedly announced, it should be - at the very least - comparable to the XBox 360 out of HD mode. Nintendo has proved they can make more effective products with less power, time and time again. The details on DS games - such, for instance, the numerous little touches in Castlevania DS - have impressed me much more than the near PS2-quality overall presentation of PSP's library. But back on-subject, the Revolution is rumored to launch at around $150, and if it's anywhere NEAR the XBox 360 or the (likely) $500-$800 PS3, the latter 2 would be in a fairly large spot in the mass marketplace of graphics-hungry middle-classers. And if it truly lives up to its codename, it will be very interesting to see what Microsoft's third and Sony's fourth hardware outing will feature.