I forgot Street Fighter 5 too, that's probably going to be a 2015 release too!

I do not think so, it is roughly 20% done according to this. It is looking more like a early/mid 2016 thing to me

http://www.playstationlifestyle.net/2014/12/18/street-fighter-v-development-currently-20-percent-complete-claims-yoshi-ono/

Halo 5: Guardians.

Xenoblade X. The first one kept me occupied for about three months and this one looks like it'll be even bigger.

Or, I could go with the idea other people have had and since that will be out near the end of 2015, I could leave that until 2016 (same with Zelda). In which case I'd actually go with Yoshi's Woolly World because it looks like it will be an absolute joy to play and I loved Kirby's Epic Yarn so much.

GT7 with out a doubt, few if any games come close to GT content wise.

I can sink 500 hours into a single GT game.

Ground zeroes was really good, but I paid half price for it. I would have been disappointed if I paid 30 for it. It's appearing to be a massive game, and I've yet to see anything that worries me about this game. Kojima only makes good games, and an mgs game has yet to disappoint. 

Zelda U

Tough call but I will go with Arkham Knight.

Everybody’s Gone to the Rapture
The Order
UC4

honorable mention to Hellblade, and Volume

Hah, easy for me. No need to mention a lot of games in my list  lol