No need to be polite here; most serious/educational games are just way too serious…and boring. Not that a good games must always be fun (though it doesn't hurt), ... Raph Koster points out "One of the subtlest releases of chemicals is at that moment of triumph when we learn something or master a task. This almost always causes us to break out into a smile. After all, it is important to the survival of the species that we learn – therefore our bodies reward us for it with moments of pleasure. [...]Fun from games arises out of mastery. It arises out of comprehension. It is the act of solving puzzles that makes games fun. In other words, with games, learning is the drug"
Where, then, is it that most learning games fail?
You'll also find a "sweet" 45 minute keynote address/video here from Gabe Newell at the 2011 "Games for Change Festival"