Pretty simple game, I can see what you're going for.
- I would say maybe move the ghost to the far left of the screen so that the player can have more time to react (or just fill/remove the open space, since you can't move back there you don't need to see what's behind you.)
- I would also make the spikes a little more distinct from the background, either with a different color or a strong outline, just so that they blend into the background less.
- Some variation might make the game more interesting. Maybe an item that gives you an extra heart, or an invincibility item or something. Or the spikes/background changing color after getting a certain score.

Simple and fun. Would like to see a more friendly interface, though!

I think the game would benefit from a slower speed at the start, gradually getting quicker as the game goes on so people who get good enough can't die unless they try to. I also think there should be some highscore counter, otherwise there's no real reason motivating people to play the game for more then 2 minutes. Finally I think the first set of obstacles should be removed so people have time to get their hand back to the arrow keys after clicking play / restart or read the instructions.

Adding those 3 points in alone would bump my rating up to a 3 / 3.5

Edit: Nice, also good call with making the obstacles get closer together instead of increasing scroll speed to, you're able to bump the difficulty even more without it becoming too fast to react to.