Uneven keys is a common sight on pianos that have not been regulated for several years. As pianists mostly play in the middle of the piano, and in certain keys. The keys do not wear evenly. It is best to observe to see if yours are level by look at your keyboard from a slight distance to see if there are undulations, and as you may also check by placing your eye level with the tops of the keys.
A key-height gauge being used on a for checking the height of the keys.