When you first get into the industry you will not be giving the glory assets, no matter how good you are. Those items will be reserved for the more experienced team members. In the game industry you'll probably be given mundane assets, like crates, or background animations, or something else that is considered grunt work. When I got in I had to make dozens of UIs with a maximum of 2 colors, black and green, and a resolution of 640x480 each. Eventually, down the road, I got to make cool stuff. Even help develop whole worlds
Again, remember that you are a part of a team. The project comes first, not your ego to make awesome assets. In most industries you will start at the bottom. Sorting the mail, organizing some asset library, monitoring a render farm, rotoscoping, etc. And they will be low impact gigs that can easily be replaced by another person. The newbies get these jobs because the upper team members want to see how good you are at what you do: can you meet deadlines? can you take direction? No matter how lowly the job appears you still have to do the best work you can do. Even if it lasts a while (if it lasts more than a year, or so, and you see no upward movement then you need to reevaluate the job).
You might also be asked to do some pick-up work that is not your specialty for any number of reasons. Usually it's because the team is short on staff and you have bandwidth to do more work. Sometimes the work may not be portfolio worthy. Don't complain, do it anyway and get it out of the way. Now, if its unethical or really way outside your expertise, that's a different story. Talk to your manager and see if there is another way. If it's something you can do then do it. The task may not be beneath you, you're just letting your ego getting in the way. The faster the mundane task is done the faster you can get to your specialized sexy stuff.
This may be different in an indie company. In that case everyone pitches in on the grunt work because everyone is on the hook to get the project done at a high quality. No matter what situation you're in, there is no room for prima-donnas.
This rule also goes for jobs you man actually don't like (until you find something new). In my past, there were companies and teams I was not a fan of. I even got passed up for promotions at one job years ago. I still did my work to the best of my abilities and I got some really good portfolio pieces. More importantly, I got the respect of other team members and made good friends. And these will stay with me for the rest of my career.