I don't think Ubuntu is the best necessarily but it has such a grip on the amount of users,it is just so much easier to begin with it. When you are happy, try Debian, which is almost the same but quirkier.

I wouldn't recommend Ubuntu past 14.04 (or is it 3).  The 15x releases are a bit unstable.

Ubuntu is so popular it even has the cheek to try to scam money out of you when you  download. You untick each donation already ticked (think ask toolbar). As you go down the list unticking they liken it as ever decreasing circles until finally you end up donating nothing which Ubuntu is keen to point out is worth exactly "nothing".  They add an "unsmiley" face to drive the point home.

But the best to start with. Just use 64 bit 14.04