There are a few major problems with modern games.
1) Too Slow
Even most racing games feel like your pushing a shopping cart around. Games like Outrun (past the first level) had hairpin turns and tight traffic to deal constantly. Turbo & Spy Hunter, accelerate like they have Rockets attached to the cars. It may not be realistic, but its more fun and challenging.
No speed = No fun = Snorefest.
2) Too Easy / No Intensity
Too many games out there are simply too easy. You walk around waiting for things to happen, and when they do, its cake to take care of. Theres no intensity. No feeling of excitement or stress. Its a meaningless romp to look at pretty graphics... which gets old soon enough.
The best memories and experiences come from challenges. Such as when I was Skiing as a kid on a school outting. Some kids piled up right on the steep hill in front of me. Couldnt turn left, as there was the lift gate. Couldnt turn right, as it was a merging of many hills with tons of skiiers heading that way. The bottom of the hill was the short, with little space to stop before hitting another gate... AND, I was not a very good Skier.
Two had stood up, and I just enough space and time to tuck between them. I hit the bottom pile, flipped over, landed flat and slid on my head. Miraculously, nobody was injured. It was a rush, and it all happened in like 3 seconds flat... but those 3 seconds were the most memorable and intense moments in the entire day... let alone much of my typical boring life.
3) Too Much Load Time. If you died in Mario, the game was quick to let you try again to keep the action going. Yet in the Wii verion, you have stupid cutscenes and long load times which break up the action... and create more of a negative experience than an addictive & fun experience.
4) Poor / Boring Controls. Sorry, but the mini analog controls are very poor for precision control of anything. There also is no original controllers such as trackballs or spinners.
5) Horrible animation. Look at the latter Mortal Kombat games, and one can not only spot how slow the game is compared to the earlier games.. but how bad the animations are. Part of the slow speed coming from animators who put too many frames in, for instance, a punch... making that punch look smooth.. .but way too slow and completely unrealistic in every way.
6) Too many explosions / Bad explosion graphics.
Many games put so much garbage on the screen that you cant even see what they heck you are doing. Also, they draw it poorly, looking nothing like real explosives. Often, they stay on-screen too long as well.
7) Same game over and over again.
Most games use the same engine over and over again with little to no real difference. The only real change is the graphics.

Pathetic game score.
Techno-like backing that has no emotional impact at all to the player. It also gets boring and grating really fast. Listen to some c64 compositions and they are amazing, even though they may not sound as good as modern instruments/synths. They actually convey emotions and have musical complexity & creativity.
9) 3d not 2d.
Sorry, but many 3d games just are not as fun, or even good looking as a well made 2d game.
10) Crazy Camera pans, slow-mo & Cutscenes in the middle of Live action.
Ugg. I dont care what it looks like to break a fighters leg in slow motion. It only serves to make me dizzy from the camera pan, and annoy the heck out of me for taking away the gameplay speed and intensity.
I would also say originality.. But heres the deal... I could play a zillion versions of the 2d supermario games... and as long as they remain challenging, with only a few changes and tweaks, they will still remain fun to play.
So, if you are getting tired of playing games... I suggest you start playing some intense games that really kick your butt (probably older mame and console games, possible indie creations). You cant get board, when every moment is living on a razors edge.