I usually just focus on about three or four games at a time, all being of different genres. I try not to have more than one of them with a deep-ish story to follow, like an RPG or visual novel. This game is what I will spend more of my time playing until completion. This could also be a long, emersive game that I feel I need to stay engaged with or else I'll lose interest. Seriously, playing just one long game at a time can be very good for some gamers.
The rest of the games I play are usually more shallow games that allow me to take a break from the longer game (if needed), and I can quickly play for short sessions and not feel lost after long absences. There's no need to know what happened in your last play session to jump back in. Games that work well at a gaming arcade work well here. Something like fighting games, racing games, sports games, or even some simulation games are fine for me.
I choose to play games this way so I don't run into the problem of starting and not finishing too many games, like you seem to have now. For many years, used to often have this problem, but fortunately, my newer way of playing allows me to stay focused and beat more games than when I'm overwhelmed with many unfinished, forgotten ones. It's almost like trying to learn multiple musical instruments or doing multiple chores/projects around the house. It's better for some people to stick with one or a few things at a time and feel like you're actually getting something done.
I never liked going back to big games after a while of not playing them, just to consider starting over.
From your list, I'd choose just one of the longer RPGs that I feel is the most interesting (or whichever one you've played most recently) and push through to the end, and one or two of the smaller, shorter games for when I need a break.
It's okay to stop playing a game if you no longer find it fun to play. If you have another console or PC, another short or shallow game wouldn't hurt if you feel a little burnt out on 3DS games. Or it could be time to move on to another 3DS game not listed here.
For motivation to beat some shorter games, take a look online to read how many more levels you have left, and use that to help push you through to the end.
Don't feel bad using a guide or not finishing anything 100%.
Hopefully, you'll watch the credits roll on them all. Good luck.
Praise Rainbow Mika
NNID: JasonMaivia ; Samurai Warriors 3 (Wii): 0346-6035-0276