This is actually quite the funny question, as traditional Chinese history usually depicts the opposite happening. In traditional tellings, the pattern will always be that the founder of the dynasty is a ruthless but pragmatic leader, thus being able to govern the empire more effectively. Over the generations, as the heirs, growing up among the opulence of the palace, lose touch with the people, tyrants and corruption would start appearing. Then finally, the people would've had enough of the corruption and misgovernance, and another great and pragmatic leader would overthrow and install a new dynasty. Rinse and Repeat.

As quick examples, the Founder of the Han Dynasty, 劉邦, is considered to be a paranoid but overall effective leader. Same with 李渊 and 李世民, the first and second Emperor of the Tang Dynasty. Both were also considered to be very effective Emperors. Similarly 朱元璋, founder of the Ming Dynasty.

Now, to some extent this is a bias caused by the fact that the history of the previous dynasty is usually written by the next, so the next dynasty has a vested interest in delegitimizing the last few Emperors of the last dynasty, and similarly has an interest in recalling the glory days of the previous dynasty in conjunction with his own.

However, the ultimate point is that, no, historically speaking in China the common occurrence is for benevolence to deteriorate across the generations, rather than the opposite.

If you have an interest in a (much) more detailed view, there's an excellent English language podcast called, The History of China Podcast. Here: https://thehistoryofchina.wordpress.com