I am watching Netflix Daredevil (2nd Season) and I noticed that whereas some executive producers appear collectively (Stan Lee among then), others are credited individually. Is there some reason for this?
Same reason everything else about their credits is formatted as it is: their contracts said so.
In the specific case of EPs, there's really three different "kinds" of executive producer for a TV show (with movies it's slightly different):
- Some executive producers are credited because they own the rights to intellectual property that requires they be given such credit. Stan Lee is one example; another is Siegel and Shuster being given EP credit anytime someone uses Superman.
- Some executive producers are financial supporters only. They pony up the money needed to make a production, in exchange for a cut of the profits.
- Some executive producers are hands-on, managing the production and given direction to the content. (This is mostly a TV phenomenon -- executive producers on movies are rarely this directly involved)
Depending on how involved a given EP is, or what they did to get EP credit, will dictate how they get credited. Typically, producers that are hands-on with a given episode will be given "more" credit that someone who was involved at a higher level; people who's EP credit comes attached to some IP might specify that they need to be credited a specific way (perhaps as "creators" in addition to EP).
Ultimately, it all comes down to finances and legalities and giving everyone what they were promised.