Here is some other performances of 2013 worth mentioning or considering for top ten:
Lupita Nyong'o as Patsey – 12 Years a Slave
Michael Fassbender as Edwin Epps – 12 Years a Slave
Judi Dench as Philomena Lee – Philomena
Tom Hanks as Richard Phillips - Captain Phillips
Barkhad Abdi as Abduwali Muse – Captain Phillips
Jared Leto as Rayon - Dallas Buyers Club
Lea Seydoux as Emma - Blue is The Warmest Color
Toni Servillo as Jep Gambardella - The Great Beauty
Oscar Isaac as Llewyn Davis - Inside Llewyn Davis
Also some part of me wants to switch Joaquin Phoenix and Christian Bale but that's probably personal bias creeping in. Not too sure about Leo against Chiwetel as well but I suspect I got it right.
Excellent idea, Timmy!
I have only one suggestion: Separate actors and actresses.
For now I agree with Sherick. I don't particulary want to separate this list into two different ones. Bruno, feel free to post male or female only list for that year or previous years. I will take them into consideration, that's for sure.