"Way better" and "way more" are popular expressions, but they both seem incorrect to me. "Far better", "far more", "much better", and "much more" all seem correct. Is this true? If so, why?
Apparently, "way" was a contraction of "away". It took on an adverbial meaning in the early 1900s:
Way can be used as an adverb, but it is very informal. According to this entry:
It is not incorrect to say that something is way better or that you have way more of something, but it is not formal. It has also been in adverbial use for long enough that 80 year olds should accept it.
I think the reason "way more" or "way better" might sound incorrect is that the word "way" is also commonly used as a noun, as in "which way should I go?". You could substitute "which direction should I go?" for "which way should I go?" but heretofore I have not heard anyone say (even in slang) that something is a "direction cool site." (I might bloody well have to eat my hat in the future but for now I haven't yet heard that instance of delightfully creative usage stretching enjoying the slang category of acceptability.) If someone is associating the noun form of the word "way" in an adverbial context (just as a matter of familiarity or habit and not by way of linguistic analysis), then the ear might reject the usage based on the fact that something seems "incorrect" when a noun is substituted for an adverb.
That is how I determined why the slang use of the word "way" as in "way more help" was unpleasant sounding to me when I first heard it. So while admittedly the ear can be deceiving and is no substitute for rigorous linguistic analysis, the ear as one of our 5 sense instruments does alert us to external stimuli that are different than what we are used to and therefore provides us with departure points for further investigation.