My first advice would be - don't beat yourself up about it.
I'm coming from the perspective of someone who is hella neurotic and anxious, of course, but even the smallest and silliest BS like "oh no I have so many games on Steam i bought but haven't played yet" is occasionally something my brain picks up and runs with and turns into something to constantly fret over. Yes, it's dumb, but that's how faulty neurochemistry does sometimes. Even if you're only having the occasional pangs of guilt, just take a moment every so often to relax and realize that you'll get to everything eventually. Games aren't like pizza, the leftovers aren't going to go bad within the week unless you desperately gobble them up at midnight while standing in the pool of light from the fridge.
Second is to just realize that for some people, things come in waves. Sometimes that wave might be "I want to play a platformer now instead of an FPS". Sometimes that wave might be "I don't want to play a game at all". I've come to realize that I'm more to the second type and tend to cycle through periods of writing *or* drawing *or* playing games intensely, which suits me just fine most of the time (but perhaps does disappoint the people I suckered into actually reading my awful fanfiction who expect weekly updates and then are greeted by a drought of a few months, but what did they really expect after Commander Shepard bought Luke Skywalker a couple of strippers and an ice cream cake inscribed 'sorry your dad's dead'; the proverbial shark was jumped quite a long time ago).
Basically, it happens. Don't be afraid to set aside games entirely for one of your other interests. Every so often, for example, games don't interest me because I just want to do something that directly affects the physical world. Sew something, sculpt something, build a pillow fort, you know, whatever. If you've got an itch that games just aren't scratching, how about trying something entirely new? Sculpt that hedge into a unicorn, learn to crochet while listening to episodes of Welcome to Night Vale, change that filter in your car that you keep meaning to do, etc. etc. Sometimes it's just satisfying to take a break from video games to get your hands dirty.
Third, if you're going to keep on playing video games, my advice - echoing most of the other people who have posted - is to try something ludicrously different from your usual fare. For example, while I like games and like discussing them immensely, I am not what you would call actually GOOD at video games; because of this, I had kinda written off the entire roguelike genre. But I took a chance and picked up FTL and I've been hooked - mostly because it's so different from my usual gaming experience that it's redefined success for me. Suddenly it's not smashing the big boss to smithereens, but instead surviving to the point where the big boss can smash *me* into smithereens. Hooray!
There are tons of different genres that are out there you may not have touched on yet. Always the good ol' point and clicks of yore, of course; if you are truly hard up for ideas, Extra Credits's 'games you might not have tried' videos are probably going to be a good place to start.
But if you don't want to entirely give up the familiar, ponder taking one of your favourite games and modding it to all hell and then playing it. I admit this may only really apply to PC games, but it's a way to give a slightly different and tweaked experience to something that's a comfortable old favourite, so you can remind yourself of why one of your favourite games is awesome while not being completely bored by having seen it all before.
Fourth is a sort of bland PSA, but again, as somebody whose brain occasionally decides that serotonin is for scrubs and losers, I figure I might toss this out here. If you've been experiencing a lack of interest in all of your interests, along with other symptoms like listlessness, trouble sleeping (or sleeping too much), and generally feeling like you've lost the ability to be happy, go see your doctor and get yourself screened for depression. It's extremely common and there's a lot of medication out there that can really help. Sometimes brain chemistry just pulls a dick move for pretty much no reason at all. There are other places online where you can take questionnaires to help further screen yourself for depression, but if you've been feeling really burdened by unhappiness not just with games, but with life in general, it's a good thing to keep in mind. Just in case.
