About the same but i'd lean towards 5th to 6th.

5th to 6th. The 7th generation significantly improved graphics while the 6th generation was a revolution.

I feel that the difference between 5th and 6th gen was the more profound for me since i remember playing FF IX and then getting X and being instantly amazed at how brilliant it looked!

The problem is that in an next generation it is not always about grahpics but that their are other factos in an gen, the 5th-6th generation was basically all about graphics. The 6th to the 7th was more about how we play games. Example achievements/trophies...Online gameplay etc;..

The 6th to 7th visual leap was remarkable but it was merely about the looks. The 5th to 6th visual leap had more impact on gameplay and storytelling. With 6th gen almost every good quality game started to have also a good frame rate, while, apart from a few exceptions, 5th gen games look like slow-motion by today standards. Before 6th gen it was almost impossible to have large scale enviroments full of animated objects like in GTA or in Jak 2. On storytelling it had a big impact thanks to facial animations, look @ the difference between MGS and MGS2 or FFVIII and FFX.

People are crazy, the difference between PS2 games and HD games is huge, I should know because recently I've gotten into the habit of collecting older PS2 games and playing them for an hour each and I was shocked by how bad most of them looked in comparison. The jump from the N64 to the Gamecube is pretty big, but it isn't as awe inspiring unless your playing the well designed Nintendo games ( Sunshine, Smash Bros. Melee, Luigi's Mansion).
Hell, I recently played Wolfenstein (2009) in SD and it looked hideous, plugged the HDMI and switched over and the difference was substantial and that's just based on the resolution.

5 to 6, easy.

5th generation was built around very basic 3D graphics, even on the relatively powerful N64. 6th generation added detail that simply couldn't be done before. 7th just added more detail.

@Doobie_wop The difference between 6 and 7 is most certainly not awe-inspiring. At the time of the release of 6th generation, I was blown away. 7 is a substantial step forward, but not surprising in any way. 6 was a huge step towards realistic graphics.

Here's a tip: don't play SD games on an HDTV.  Everything gets all smudged-looking.

4th to 5th

I was actually coming in here to say 6th to 7th was the bigger leap but then I actually looked at some of the videos and changed my mind to 5th to 6th.

Hopefully these pictures will put the jumps into better perspective.

I tried to pick the best-looking FPS of each gen, I may have missed some games.