Hetaoni is an INCREDIBLE series! It has a little bit of everything, comedy, drama, horror, complete-and-utter-heart-destroying-sadness...you know, something for everybody. To be serious though, it is a very well-written series, and the characterization is interesting (even though some characters are just a little OOC at times, for the most part, they're pretty in character).
As for the story itself, it is genuinely tear-jearking, despite using characters that were originally from a comedy series. However, given the nature of the characters themselves, as anthropomorphich (butchered spelling) countries, I guess the point of Hetalia being a comedy (for the most part...) is moot. Still, many of us have grown to really love these characters, and watching them be slowly hunted down HURTS. It's even worse when you realize that ITALY, sweet, cheerful, afraid-of-everything Italy, has been WATCHING THEM DIE FOR YEARS IN THE HOPE TO SAVE THEIR LIVES. Even worse then that, is to watch him slowly lose both his memories and (we assume) his sanity. To watch a character like that just slowly break, is really REALLY painful, even if you aren't a big fan.
Truth-be-told though, I didn't really cry that much...at least, I didn't until it was noted that Italy was losing memories ("When did I first meet Germany? What was the alliance that bound us together? And, when I was young...I made a promise to somebody, didn't I?" made me BAWL). From then on, I was in tears at the most dramatic scenes, which are all very well written. The most popular (read, most talked-about, written-about, and drawn) death scene, Italy's, is, on its own, VERY VERY well-done, and really makes the viewer's heart shatter.
I could on for a long time about the "game" but, I'll finish quickly. There aren't many flaws, save a few plot holes (DOOR+WEAPONS=ESCAPE), and the derpy icons (which were done away with, thankfully). As for other things, the sound-track is pretty good, and the gameplay's fun to watch too. If anything though, what this series is really good for, is artistic fuel. This series alone has produced so much beautiful fan-work. Go ahead and type in "Heta Oni" on Deviant Art
sometime, you'll find some really good stuff. Overall though, I enjoyed it, and, admitted, have written a few fics about it, and I recommend it; just be sure to bring tissues.