2015 was without doubt a perfect year for SM, both for great music and concepts.
EXO: they released the pathcodes to promote their full album exodus, quality album and SM outdid itself with an amazing concept, with call me baby and love me right being high quality title tracks
RED VELVET: they released ice cream cake and dumb dumb in the same year with a good bubbly and quirky concept. The red was their first full album filled with good songs
SNSD: they had a grand comeback with a full album and 3 title tracks in the same year, well studied concept by SM
SHINee: they released their full album Odd with View and Married to the music being title tracks, both great musically and with a good concept
F(X): they released their last full album with 4walls leading as the title track. A great experimental quality album done well as expected from them
BoA: she released her full album Kiss My Lips, another great album coming from her
Taeyeon: she debuted with her first mini album and I was the perfect title track to debut for as a solo artist
To end this thread, all SM's artists had hits in 2015 and all their comebacks were well received in Korea and internationally.
Do you think SM had a golden year in 2015?
What was their best year for you if not 2015?