Fifth generation:

The sheer number of ground-breaking titles is astonishing. It was the advent/rise of 3D graphics in games which meant devs ahd to think up new control schemes and games pushed lots of new ground.

Started this gen: Gran Turismo, Tomb Raider, Resident Evil, Metal Gear Solid (yes I know, Metal Gear was out before), Half-Life, Starcraft, Age of Empires, Unreal.

Look at influence of this gen:

• Half-Life: start of a huge and revolutionary shooter franchise, introduced proper storytelling, AI, proportional damage, puzzle solving etc. in the FPS genre, gave birth to Counterstrike, Team Fortress, Day of Defeat and a huge range of user mods and later Steam
• Gran Turismo: Really the first driving sim to release on consoles, was that start of a 5 game series with each selling nearly 10 million copies
• FFVII: First FF to release in Europe, showed JRPGs could be popular outside of Japan
• Goldeneye: Revolutionary and showed FPS could work and be popular on consoles
• Zelda: OOT: First 3D Zelda and is still considerred one of the best games created by many
• Resident Evil: Popularised the Survival-Horror genre and started a franchise that's still going strong today
• Silent Hill franchise started this gen
• Metal Gear Solid: Amazing storytelling and popularised the stealth-adventure genre
• Tomb Raider: started this gen and showed there was a market for a platform game with mature undertones (although likely played by pubescent teens!) Likely influenced Prince of Persia and Uncharted.
• Mario 64: Great platforming game which laid the foundations for all 3D Mario games.
• GTA and Driver started this gen and sowed the seeds of the sandbox games of later gens
• Introduction of analog stick followed by the dual analog control scheme utilised by every console since
• Introduction of rumble
• Tekken and Virtua Fighter games started this gen
• Starcraft came out this gen and went on to sell > 10 million copies and spawned a sequel. Bacame a national sport in Korea
• Age of Empires released this gen and spawned a 20 million unit selling franchise.
• The popularity of Quake II online signalled the rise of online gaming with MP focused games like Quake III Arena, Unreal Tournament and Counterstrike and becomming hugely popular
• Unreal franchise started this gen
• Baldurs Gate released and the advent of Bioware as a top WRPG developer
• Original Fallout games released this gen

I'd say the last two gens owe a lot to the minds of the fifth gen.

Metal Gear in 1987 and Metal Gear II solid Snake in 1990 on the MSX2 already popularized the Tactical Stealth Action Genre.

Metal Gear Solid was basically Metal Gear 3and had the same amazing story telling as the two before it. the only new ground it broke was to bring the Tactical Stealth Action Genre in to 3D. 

Can you name any stealth games that came after the original Metal Gear games? It only introduced a genre to the market. The fifth generation established and brought it to the mainstream. Metal Gear Solid was a big part of that and really brought the stealth genre into the mainstream audience. It also helped push modern storytelling techniques incorporating a a variety of different methods normally associated with movies.

Stealth mechanics were around to varying degrees in games, but they really took off  in the fifth gen. Games like Thief, Tenchu and Metal Gear Solid gave rise to a number of stealth based games. Many other games started to feature stealth mechanics due to their popularity (sometimes very poorly as in Tomb Raider: Angel of Darkness).

If it wasn't for Metal Gear Solid and the success of stealth games in the fifth gen I doubt Splinter Cell, Deus Ex, Chronicles of Riddick, and Assassins Creed would play the way they did. Hell, they may not even exist.

1. Just because here might not of been meany Game Designers using Stealth Action Gameplay doesn't negate the fact that Metal Gear and Metal Gear II Solid Snake were popular Games.

2. as I stated all Metal Gear Solid did diferently from Metal Gear and Metal Gear II Solid Snake was 3D stealth Action if you Play Metal Gear II Solid Snake you will see that Metal Gear Solid is basically as modern 3D Version of that Game. 

3. DEUS EX would have existed without Metal Gear as it was inspired by Ghost in The Shell and other such media. 

1. My original point still stands. Metal Gear and MGII: Solid Snake weren't as popular or influential as Metal Gear Solid. They were popular, but the effects they had on the industry weren't as profound. They laid much of the ground work for Metal Gear Solid, but there impact on the overall industry wasn't as huge.

2. I never said otherwise. I only stated that Metal Gear Solid has had a bigger impact on the industry as a whole.

3. I'm sure it would (I said some of them MAY not exist), but would it neccessarily have implemented stealth as such a big gameplay mechanic if it hadn't been for the stealth genre taking off? Thief likely had a much greater influence than MGS, but my point from the start was that the fifth gen was where the stealth genre took off, impacting many great games and it's influence is still being felt today. Metal Gear Solid was simply a part of that.

Also, Deus Ex had many great influences and saying "it was inspired by Ghost in The Shell and other such media" is doing it a major disservice. Deus Ex was influenced from a wide array of dystopian literature, modern day conspiracy theories, real-world scientific theories, graphic novels, Greek mythology, and animation. However, I was talking about gameplay mechanics (stealth), and it's primary influences were System Shock 2 and Thief (as well as more general RPGs) in this regard.