Here are ideas to make your game more exciting.
Complete your game Edit
This should be obvious. No one wants to play a unfinished game.
Make sure that the character can pass through the game Edit
The character cannot pass through spaces that are not 2 blocks high. Also, he cannot jump higher than 5 blocks. You should test your game before publishing it. You could be surprised.
Add a rhythm to your game Edit
Do not add the same let on the way too much time in a row (ten bombs in a row, ten gaps in a row). It is boring. Vary the challenge like in RUN!. For instance, three times bombs, one time a gap, two times bombs, one time a gap... Do not create the same difficulty from the start to the end of the game. Increase the challenge step by step like in The bridge.
Give some choices to the player Edit
You can add branches on the path like in Choices. One way may be quicker but the other may be easier. Add some elements to distinguish the two entries. Do not create identical entries which force the player to randomly choose a way which is boring. Add different items in order that the player can guess what it should find after. Remember that the character sees up to 8 blocks to the right, to the left, above and below. It can spoil the game.
Avoid pointless items Edit
One might be tempted to add pointless items in some places to fill the space. The player experience would teach you that it is a bad idea. Unless you are creating a labyrinth, it is boring to come into a place where there is actually nothing to do. For instance, everything has a use in Zelda. So find a feature, even visual, for everything you add in your game like in Castle.
Do not come to the excess Edit
When creating a video game, most of the teenagers are tempted to create excessive items. Going further does not always mean getting better. Doing so, the game is losing sense. So do not create the longest game, the highest wall or the biggest amount of bombs. Your game will become more interesting with originality and subtlety.