What is an ojousama-ge? It is fairly simple... it is a VN where multiple heroines (sometimes all or most of them) are young women from wealthy families. I love these VNs... but it isn't so much because I like ojousama heroines (though there is that, since I love people with warped personalities). Rather, it is because some of the best charage, nakige, and non-action story-focused VNs I've played are ojousama-ge.
Otome ga Boku ni Koishiteiru 2
Haruka ni Aogi, Uruwashi no
Akatsuki no Goei (the first one only, since 3 varies its heroine types a lot more)
Otome ga Tsumugu, Koi no Canvas (and the FD)
Ojousama wa Gokigen Naname
Now we come to why these VNs tend to be more likely to be good... and the answer is relatively simple. To be blunt, settings where multiple ojousama heroines are possible tend to be a bit more detached from everyday life than the average VN setting, thus giving the writer more flexibility to form the plot of the various routes and overall VN. Another aspect is that people with money tend to be the target of all sorts of problems, from simple marriage issues to kidnappings and assassinations. As such, it is very easy to create an exciting story that feels relatively realistic in such a setting.
It is pretty easy to see from this why I generally get excited about ojousama-ge, now isn't it?