You know, playing this type of game takes a lot of time... Generally it takes about 20 hours to play one game. Some games like "Fate/Stay Night" or "AIR" needs about 40 hours, and it would not be problematic if the game is interesting.
The misery is when the game is way too short and nothing interesting. Unfotunatery, there're many many that type of game... they are called "mine" because you can't tell until you buy it.Actually, there're many sites evaluating Ero-Ge, thus if you wait to buy games until the rumor comes, you can avoid to get "mine" games. However, some game lovers are so frantic about collecting newly marketed games, that they get handful of mines. They are like mine-sweepers (^^;
Rumor of games on the internet critically affects the sales of games. For example, games like "Tsukihime", everyone knows today, is not at all famous at first. Today's market of Ero-ge owes much to those mine-sweepers!
External Link: Erogamescape, a famous game evaluating site