I frankly believe that someone's code is better when it's easier to change, debug, navigate, understand, configure, test and publish (whew).
That said I think it is impossible to tell someone his/her code is bad without having a first go at having him / her explaining what it does or how is anyone supposed to enhance it afterwards (like, creating new funcionality or debugging it).
Only then their mind snaps and anyone will be able to see that:
- Global variables value changes are almost always untrackable
- Huge functions are hard to read and understand
- Patterns make your code easier to enhance (as long as you obay to their rules)
- ( etc...)
Perhaps a session of pair programming should do the trick.
As for enforcing coding standards - it helps but they are too far away from really defining what is good code.
