Specifically, I will be drawing from my own building experiences. Admittedly, regrettably, I still have a few 2015 sets unbuilt. I don't want to become the AFOL stereotype of having hordes of boxes of unbuilt sets. These are not yet built because I thought I'd review them and then I never did and then I realized that Jurassic World sets and Quicksilver's Avengers set would never be on store shelves again after their initial run. But I doubt they'd make this list anyway.
The list of my favorite sets stars off with General Grievous, who has a fantastic build and looks great on my shelf. That's saying something, because it's hard to be surprising with constraction sets nowadays, and because I like to think I cannibalize my sets pretty quickly after getting them if I'm in a building phase. But until I build a tan Bionicle MOC, Grievous is here to stay. People can argue about the price, but for the satisfaction of a 45 minute build that is quite intense, it's worth it.
I also had the pleasure of building the Helicarrier with 55555 thanks to Toa Lhikan Hordika buying it and then we did a livestream to build it. Good times. It's huge, it's iconic, it has a great build. And I didn't pay for it but got to build it anyway; you'll have to ask TLH if it's worth the $350 plus motor pack. (I bet he'll say yes.)
The Doctor Who LEGO Ideas is also worthy of a mention. It's got the minifigs, it has the TARDIS interior and exterior, and it's reasonably priced for a licensed set. Unfortunately it doesn't come in numbered baggies for staged building within the instructions, which means you are searching for parts a lot longer than expected.
And finally, I can not forget the Millennium Falcon! It's iconic, has a great build, comes with great play features and hosts some great minifigs. I'll be keeping this displayed on my shelf for at least a year before realizing I need grey angled plates for something.
These were my favorite. I build some more, but nothing as stand-out like these. I've already got my hands on a ton of 2016 sets however, some of which already look amazing, and some which can be criticized too. Now to find time to build some....