All a five gallon starter kit will allow you to do, is to make 5 gallons of beer.
It's really not the gear, or the method that makes the best beer, it's the brewer, and his process. A skilled brewer can make award winning beers with a mr beer kit. There have been a few on here who won categories is BJCP contests. If you look at the tips mentioned throught the forum and especially the above mentioned thread, you will make great beer regardless of whether or not it is in a 5 gallon batch or a 2-2.5 gallon batch in the little brown jug.
Whether it is good or crap has nothing to do with whether it was done as a mr beer, or a 15 gallon batch on a herms system. Or whether or not it was extract or all grain. Just the skill of the brewer.
I've choked down plenty of crappy AG beer that was done in 5 gallon starter kits, or on fancy systems. And tasted some really great mr beer beer, done by a skilled brewer......