Ubuntu, Ubuntu and Ubuntu. LOL
Ubuntu and it's variants(Oh I hate that word now) really are the best for the general public. Anything else is for complete nerds and if you try to get help, they turn into very nasty little nerds.
I've looked at all the non Ubuntu lightweight distros recently and they're all weird in some way. Linux Lite isn't half bad. Peppermint OS also. The rest are for the fore mentioned nerds.
Xubunt & Lubuntu are pretty lightweight yet main stream enough to have plenty of usage, plus, general Ubuntu support works for most things. You can type a question into duckduckgo and half the time, the answer will show in a block to the right of the general results. That block will be based on an answer from stackexchange or askubuntu
Coolest thing about the Ubuntu, Mint, and Elementary is the software management tools hooked to the Ubuntu software repository. Loaded with tons of Apps for everything.