How to combine two files into one with columns for each file's data?

You can use paste:

$ :|paste -d',' file1 - | paste -d' ' - file2
1, John
2, Sam
3, George
4, Ken

or:

$ :|paste -d', ' file1 - file2

where the -d', ' argument specifies to use a comma and space as a delimiter between the contents of each file.

Another paste solution

paste -d ', ' file1 /dev/null file2
1, John
2, Sam
3, George
4, Ken