There's a website that holds an internet poll every year to pick the top 10 4koma manga releases each year, and 2015's results have been announced.

The top 10 in the newcomer category (newly-started series whose first volume released in 2015):

1. "Machikado Mazoku" by Itou Izumo
2. "Kyou no Noruma-san" by Fukasaka Emi
3. "Nomijoshi" by Ukatsu
4. "Nakahara-kun no Kahogo na Imouto" by Hoppege
5. "Swap⇔Swap" by Tomekichi
6. "Blend S" by Nakayama Miyuki
7. "Kamisama to Quintet" by Oshioshio
8. "Sunohara-sou no Kanrinin-san" by Nekoume
9. "School Architect" by Kikai
10. "Custom Maid" by Tachitsu Tetsuko

The top 10 in the ongoing series category (ongoing series that had a new volume released in 2015):

1. "Yuyushiki (volume 7)" by Mikami Komata
2. "Hakoiri Drops (volume 4)" by Tsurusaki Yuu
3. "Hidamari Sketch (volume 8)" by Aoki Ume
4. "Gochuumon wa Usagi desu ka? (volume 4)" by Koi
5. "Slow Start (volume 2)" by Tokumi Yuiko
6. "Star Mine (volume 6)" by stroma
7. "Kiniro Mosaic (volume 6)" by Hara Yui
8. "New Game (volume 2)" by Tokuno Shoutarou
9. "Shimekiri Gohan (volume 2)" by Konishi Aki
10. "Hitsugi Katsugi no Kuro (volume 5)" by Kiyuzuki Satoko

The ongoing series category is almost exactly what you'd expect, though there are a couple titles that I am a bit surprised aren't on it (A-channel's down at #17, it seems).

The newcomer list surprises me a bit because while I enjoy Machikado Mazoku, I wouldn't place it as the best of the year. I also don't think School Architect is anywhere near as good as a lot of others seem to. I do really enjoy Blend S so I am happy to see it there, but it's het so probably not of much interest to most here.

Pretty much every major release is somewhere on the full listing. Name a series you're curious about and I'll look for it for you.

(Yes it's basically nothing more than a popularity poll, but I still find it interesting. Especially in noting how many of these I've read (way too many))

where does sakura trick rank?

Sakura Trick seems to have had two volumes released during 2015. Like pretty much every other instance of this, the more recent one ranked much higher.

Volume 6 is 77th and volume 5 is 113th.

I'm glad for swap swap, really like that one, it's hilarious