Borderlands. Loved the heck out of 1 and 2 as they were new, never could ever get into Pre-Sequel and bounced off of 3 real quick despite being optimistic about it in its lead-up to release. I sort of feel like the entire tone of the series and its loot carrot core aren't doing much at all for me anymore.
Gears. At one point, I admit, I thought Gears was perhaps my favorite franchise on the market from Gears 1 thru 3. I thought it played excellently and had amazing visuals for the Xbox 360 era -- while their incredibly high standing in my eyes has diminished with time, I probably won't ever forget that at one point in time, I did hail the series as one of my absolute favorites. Judgment, 4, and 5 have not captured me anywhere near as well. I haven't even beaten Judgment or 5, and I really had to force myself to wrap 4 up. 3 felt like a really good place for the story to stop, and 4 hasn't done anything terribly interesting to me from a gameplay or story standpoint, though I do like the characters and the updated visuals... But they haven't been enough to keep the old love I had for the franchise and I think I just gotta let it go now.
Destiny. What a roller coaster this franchise has been for me in terms of engagement and interest. This generation, it's been responsible for some of the most fun and addictive spurts of interest I've had at times, and at others it's just felt tired and lifeless as an experience. I last played at the launch of Destiny 2 vanilla and haven't gone back, but the way I see ongoing conversation going with that game, it feels like it's the same old song and dance -- on the up on one update, then pissing off or boring fans to death by the next one.