Do I have the right to be mad and should I quit my job?

So basically I work at a restaurant/pub and many of our bartenders will be leaving in the next coming of months.

I've been working there for almost 2 years, helping out bartenders as a server and learning about our drinks in my spare time. When we get new bartenders we actually don't look for people with bartending experience but usually just some servers who show excellence in their position.

The 4 people they decide to train.

(Steve) (19) works 40 hours of week on top of school, hard worker, has been working at our place for 5 months.

(Mary) (19) sister is a bartender there, has no clue about any drinks, Has been working here for 7 months.

(Emma) (25) One of our worst servers, always lost in space but somehow is being offered a bartending job.

(Christine) (19) has been working here for 5 months and has asked me what a jack and coke was at one point.

I just feel disrespected, this is a job I always expressed interest in and I feel the people they're promoting besides Steve don't deserve it.

Again I'm 21,I'm in college and have been working there for 2 years and I'm thinking about quitting once I can get a bartending job somewhere else. My name is Mark