The Star System on Retro Bowl is used to represent how well a player can perform based on their Attributes. The star count ranges from half a star to 5 stars, 5 being the best.

A LB with a star rating of 5 could look like this

A DB with a star rating of 5 could look like this
Players with higher stars will appear higher in the free agent list, and cost more Coaching Credits.

A WR with a star rating of 5 could look like this
Players with higher star counts will also be more common in the first round of the draft. These players are more often "picked" by other teams later on. [TIP: Players with not as high star counts in the draft may still have high Potential, be sure to scout them!]

A RB with a star rating of 5 could look like this

A QB with a star rating of 5 could look like this
Players with stars will always perform better than players without stars, the only way you can get players without stars is when you have an empty position on your Roster, and a substitute will fill in for that position. Said substitutes have minimal attributes and are generally much slower and weaker than players with stars. All players with stars that you have will be shown on your Roster.