What's the point of opinions? They can be biased, misleading, coming from user mistakes and other questionable origin. Since you seem to be new to the topic you should focus on reviews done in systematic way under controlled conditions.
First you could have a look at the Canon lens line up, secondly you can check the price list here to get ideas about third party lenses commonly asked about. Additionally, the websites of the lens makers have plenty of details.
Common review sites: www.dpreview.com;www.photozone.de and many others. Just google for "[lens type] review" and read.