Here is diagram published on TechCrunch about the financial returns of angel investors. There are 2 ways to improve the diagram:
  1. Make it a simple stacked column diagram that adds up to 100%, 1 column for the US, 1 column for the UK next to it.
  2. Use more contrasting colours than the dark blue and red
Then there are a few more things you can do to make it look less like Excel: tick marks out, big title at the top left, replace the Times Roman font from something sans serif, value axis title below the main title (i.e., no vertical text).