We have so much various languages. It would be perfect to have only 1 speaking language.
Oh no, that would kill all of the diversity on this planet!
On the other hand, have you ever heard of the story about the "Tower of Babel"? You should read a little bit about it to understand how the diversity of langauges originated.
For me it wouldn't be perfect. The world would be somewhat boring. As Lucas pointed out, languages are the most representative form of culture. Also, they are challenging and it makes language diversity an amazing thing.
I hope not!
It's like saying "I wish there were only one pasta and cheese in the world". Delicious indeed, but they would become boring after a while and they certainly wouldn't cover the whole range of nutrition and taste.
languages are fulfilled with culture in all levels. and the languages are always changing. because the people who speak it put their habits and thoughts on what they're speaking.
I can't say the same sentence in various languages without considering the cultural difference between the people around the world. I'm not talking about just food, but environment, boarders, races, belifes, etc...
Even the same language will not be spoken in the same way by two different countries, and we can see that:
British English - American English
European Spanish - Latin American spanish
European Portuguese - Brazilian Portuguese
France's French - Canadian French
They were the same once, but the inevitable happened, the people changed the language, and they are still changing. I bet, the Slovak spoken today isn't the same that the Slovak spoken 100 years ago/200 years ago
If everyone in the world woke up tomorrow speaking the same language there would be a lot of language teachers on italki without a job. :D