These tasks can be addressed in any order:

Prose

• Focus article on the character Sonic, and his creation and evolution. Reduce discussion about the games in general
• Edit sections from an out-of-universe perspective where possible.
• Copyedit sentences with redundant words. (See: How to satisfy Criterion 1a)
• Replace references to concept-mobius and ghz with suitable (quoted) references using {{cite video game}} where possible.
• Remove fancrufty comments about speculation and fan tastes. (e.g. is Shadow or Metal Sonic more popular, etc.)
• Remove original research. (Metal Sonic's current location, reasons behind talking, etc.)
• Reformat external links in the text as footnote references.
• Clean up the article to use the same person, in particular, do not intermix you/we.
• Use the dash guidlines consistently.
• Use consistent punctuation.
• Add Ryan Drummond to the "Voice portrayal" section. He was the official voice of Sonic for six years and yet he's mysteriously absent in this section.
• Remove pointless lists.
• All plot should be written in present tense.
• Add overall article template for all Sonic character articles for uniformity
• Remove the fact that he is uninterested in martial proposals from Amy Rose. You never know...

Images

• NB: Try to make sure that downsized transparent PNGs do not have a black background in IE.