Yikes, I know that feeling. I have an obscene amount of games but some days I just don't want to play a single one of them. It usually happens when I'm too tired and/or it's too late to commit to one.
Anyway, I'm currently playing Elite: Dangerous (Solo) with The Witcher 3 sprinkled in between :)
People say Elite: Dangerous is like a vast ocean with the depth of a puddle. I don't disagree with that assessment, but it didn't stop me from enjoying the game either. I think what appeals to me is the flight model. Of course I haven't played many space/flight sims long enough to say that ED's way is innovative, but the ones I have tried don't have quite the visceral experience that this game has. It's not just the way the game portrays the physics, it's the sound design too. Hearing your ship whine, groan and rattle during various maneuvers really sell the idea--the feeling that you're flying a spaceship...and having a HOTAS (hands on throttle and stick) helps too ;)
As for The Witcher 3, I found I enjoyed it more than I initially expected. Almost everything I do in that game is interesting, including side quests and sailing in a little boat :) The side quests seem more interesting to me because it feels more dynamic. It's not straightforward. While it still have fetching and escort tasks, it's not the main attraction for these quests. Side quests in this game feel like short stories you're embarking on that takes place in the same world.
Its combat mechanics is similar to Assassin's Creed's combat mechanics, but there's more variety through the use of signs (basically quick cast magic spells), bombs, potions, etc. I find myself using almost everything available to me during a fight. There's definitely strategy involved in the combat as well. In the end, when I win a fight I feel like I accomplished something.
This game doesn't make you grind for potions and oils (weapon damage buffs based on the enemy type). Most of the time when I harvest plants, it's to make a new potion/oil (or upgrade them). They have a system where replenishing them doesn't involve going back and forth to look for specific ingredients. If you're the kind of person that tries to loot every container you see, you're pretty much set.
This is a game that felt like it was designed by thoughtful gamers. Of course that's just my experience with it and your mileage may vary.