I think a key element in making an RPG fun is the sorts of choices that players get to make about their characters. Having a choice system that is both simple and highly variable is excellent as players get both the joy of making characters quickly and doing so without high system mastery requirements and also the entertainment of having incredible variety so characters can all feel unique. The obvious question: How do you build such choices into an RPG?
The technique I champion is to give players choices where they are always picking from a list of ten or less things. When players need to flip back and forth through huge tables or lists they get overwhelmed and almost universally feel like they must have missed something. Usually that feeling is right. What they really need is not a computer aid to sorting through interminable lists but rather a low number of options that are all decent. Choosing a race and class in old school DnD definitely worked this way as there were six to ten of each and so they were all well differentiated and easy to hold in your mind while choosing. Both DnD Next and Heroes By Trade do the same thing because in this case the classic model is a good one.
Feats on the other hand are a real problem in both old DnD editions and Next. The list of them needs to be huge because they are so specific but that creates choice paralysis in new players. Both in the old days and the new there are lots of trap feats that are utterly rubbish so careful perusal is required and system mastery is necessary to avoid just being bad. When feats were first introduced I really liked the idea as a way of adding customization but now that I see where it leads I like it very little. Any time an important aspect of a character comes down to "Here, read this book of stuff. One of the things in the book is super broken but it isn't obvious which. Have fun choosing!" it has failed.
Next manages to fall on the unfortunate side of feat design because it has too much choice and on the wrong side on class design because it has too little. Each class is built with a singular option that makes the great majority of your decisions for the future for you so although you have a few different things you can do (which is great) you end up not getting to make decisions in the future which leads to a stifling of variety. A good example of character design is more like the World of Darkness system where you consistently get a number of points to divide amongst a small set of choices. All those small decisions multiply together to generate incredibly diversity but each stage is straightforward. This means the new players can get started easily and without being lost and the optimizers have plenty to work with. Of course the mechanics behind the WoD numbers are a mess but I admire their character sheets at the very least.