Actually, quite a lot of Saturn games are still very good. E.g. Radiant Silvergun (also many other shooters), the 2d fighting games (SF Alphas(Zero)/KOF/Vs./etc), others (Dragon Force)

PS1, I haven't really played lately, but yeah Castlevania: SOTN is still great, Final Fantasy Tactics, can't think of any others off the top of my head.

Never owned an N64, so...

I think certain games lose their appeal as they get older. I don't think many people want to relive a PS1 Madden for instance. I think games that only had appeal because of advancements in technology, like say the original GTA for sandbox gaming, don't really add up too much anymore since the formulas been improved 10x over. Something like Metal Gear Solid however broke grounds in storytelling, and I still don't feel it's been topped by many games, if at all. Castlevania was the epitome of 2D gaming, so as that continues to die, it will look better and better. If 2D gaming were still prominent, I don't think we would be selling as many praises for SOTN anymore. Light gun shooters age well because they don't advance much. Side scrolling shooters like Einhander havent aged a day because the genre is near death. Gunstar Heroes will always measure up because Treasure is legendary and what they create defies time and age. 2D fighters have advanced slightly since those days.

I think ChichiriMuyo nailed it better however. You're going to see these games for what they meant to you at the time. I look at No Mercy(my fav game ever) and I don't see horrible collision detection, an outdated roster, bland visuals, horrible sound, etc etc. I go back to 2000 mentally and the game feels as fresh as ever. Your mind is funny that way. This is also the reason why we can stand to look at DS graphics and say we're getting something great even up against the HD consoles. It's all about perception. 

Certain games have aged well: Mario Kart 64 is still very fun even by today's standards. Fighting games haven't changed much either since that generation, so a game like Tekken still feels current (in terms of gameplay, not graphics obviously). With the fifth generation of consoles, 3D gaming was introduced as the norm, and all the best games in the current gen are basically just upgrades, of these first 3D games. Halo is just a souped-up Goldeneye, GTA4 will be the same as GTA1, and Mario Galaxy could just be called "The New Super Mario 64".

The N64/PSX/Saturn generation was and remains the worst in gaming history. Most of the games haven't aged well because they were crap to begin with, although there are some really outstanding games from that period like SotN.

Graphically, it aged horrendously. The PSX and Sat being worst, with the 64 not quite as bad. Early 3d was a learning era for gaming, and a lot of games got things wrong. Some games are outright painful to look at now.

Gameplay wise, not as bad. Some games are incredibly dated by poor controls and the like, such as RE, but others have stood up very well.

Soundwise, eh. I'd say the N64 is the worst with terribly MIDI, but some of the PSX games had terrible butt rock. and just cheesy soundtracks. Others were orchestrated and outstanding. Then again generated chiptunes > cheap redbook.

My ps works great and so does my n64

I still can enjoy great games from that era. Ocarina of Time is still my favorite game of all time.

The fifith generation was awsome. It cannot be compared to any other. It had the best games, the best consoles, and the models of the future. They have aged pretty well. I still play my N64, and PSX today. It was an amazing time for games.

Teh 4th and 5th gen. was the birth of many great series of games. Like Super Smash Maro kart super mario 64 stuff like that...

this generation is the beginning a new control scheme