My top 5 game list
5)
Audiosurf 2
Why did this game came in my top 5? Just for the reason I'm addicted to music and to play a game based on this one is just excellent, it's still in beta test but so much potential...
4)
Sang-Froid: Tales of Werewolves
For the same reasons as LoathsomePete, if you can try it, do it!
3)
Guildwars 2
I know it came out in 2012, I had it the day of the release but it wasn't as good as expected (again), and I left it for like... 6 months and took it back after that, it changed so much from the beginning that, for me, it is a game of 2013
Not gonna say it's better then the first one, the difficulty is too low but it's one of the greatest games in my opinion.
2)
Antichamber
Like you said, 2013 was the year for indie games, this one was by far my favorite, a puzzle game in 3D... Cannot describe it so strange it was to play it ^^ Just one thing, if try it, prepare your mind to explode
1)
Factorio
Again, an indie game, by far my favorite of this year (or I forgot some ^^), one of my favorite real-time strategy games/management games, to try if you can
My most disappointing games of 2013:
Agarest 2
Amnesia: A machine for pigs
The games that didn't make it in my list 'cause they were made too early
Dwarf Fortress (one of my favorite games of all time)
Tales Of Grace F
Dark/Demon's Souls