Having done way too much pulling of logs with a come-a-long I gotta say its brutally slow but gets the job done. I was gonna mention snatch-blocks also but I see both you and @johndoer123 already beat me to it!
My personal tricks involve a small device I came up with that has two wheels on it that I fasten with timberloks (landscape screws) to the log at the rear so it can move easier. It is terrain dependent but works well when applicable.
The other trick is using a zip-line with a pulley on it to hang the front of the log on so it does not drag on the ground when being pulled by the come-a-long.
Both approaches require a little extra work but whoa when the conditions are right for it they make a world of difference on the load and dramatically decreases the energy (calories) it takes to move it.