I recently flew SFO/YYZ/(SCL)EZE. This was in the front cabin, and it wasn't bad. AC seasonally has YYZ/EZE nonstop service.

Your best bet to EZE is generally going to be on LAN, as far as service goes. (Again, you don't mention what cabin you will be in). Unfortunately, they got rid of the LAX/SCL nonstop. However, to EZE, that isn't the end of the world - fly SFO/LAX/LIM/EZE. Your LIM connection is about midnight, and you get a nice 8 hour LAX/LIM leg. They have a great IFE system. LAN pricing generally includes the SFO tag on AA or UA. The big downside is the LAX connection on the return, which makes that last hour turn into 5. Despite this, it is how I usually go.