I am trying to understand one thing about the quality of links on websites ...
Let say I have 2 websites that link to me and that my website talks about "green widget "
The 1 st website that links to me has a title tag that says " green widget " in it, it has a page title that says green widget, the content of the page is green widget , the www.webaddress.com/isgreenwidget but the PR is 0
The 2 nd website that links to me has a title tag that talks about "the color of the sky " ( so nothing related to green widget ) it has a page title that talks about " the color of the sky ",the webaddress.com/is/links or / colorofthesky but the PR is of 5 ...
What page will be the most useful for my ranking and what page will google give more importance too ?
There are lots of other variables - such as how many links are on the linking page, where the link to your site appears in the page's structure (in the content is by far the best) and so on. Still, since PageRank is roughly logarithmic a URL with PR5 is a LOT more than five times as strong as a PR0, and it's more likely to offer the best ranking help.
Except for one thing - why would a strong PR5 page want to link to your site if it's not on the same topic? That doesn't sound like a natural link to me, and it might just be ignored by Google if their algorithm assesses it as an unnatural or paid link.
as ted mentions there are many variables at play. a simple rule of thumb is if you a link will deliver relevant traffic to your site then its a good link. if a link wont deliver relevant traffic to your site you are probably wasting your time and/or paid link budget.
personally i dont worry too much about which link is more powerful since you generally need many, many links to rank in google. instead of deciding which link to get, it might be smarter just to pursue both links.