Colonialism ruined whole countries leaving them poor, rewrote cultural narratives, uprooted entire social structures and in a word, destroyed peoples histories and a sense of their own independent identity. In the bloody aftermath some flourished and some did not; but this cannot be used as an example of the "superiority" of certain forms of government when the existing forms had been destroyed.
A good starting point on further research is the book; Why Nations Fail: The Origins of Power, Prosperity, and Poverty by Acemoglu and Robinson (be sure to read the Critical Reviews section) - https://en.wikipedia.org/wiki/Why_Nations_Fail
The following two videos though dealing specifically with India under British Colonialism are equally valid as to what had happened to other countries under the British Empire;
1) W.r.t. what British Colonialism did to India, see Dr. Shashi Tharoor's longer speech Looking Back at the British Raj in India - https://www.youtube.com/watch?v=OB5ykS-_-CI
2) Shorter version of above at Britain Does Owe Reparations[to India] - https://www.youtube.com/watch?v=f7CW7S0zxv4