I'm in high school and have been dating this guy off and on for almost a year. He's great, I mean, I love the guy to pieces but our relationship has been very plain and flat for many months. I mean, he doesn't laugh at my jokes or act enthusiastic with me at all anymore. He's been very predictable and it has become quite boring.
So now I've met this new guy that I'm really interested in and seems to be someone I'd have a really good time with. I'm 15, and I feel like I need to stay in the long term relationship, but at the same time I'm ready for something new. I need a fresh breath of air.
I really just do not know if letting the long term relationship is worth the outcome.

Any advise or input?

At 15 you don't need to worry about long term relationships. Have fun. If things are not working with your present guy and you have met one you'd like to get to know, go for it. Present guy is probably bored with you now too. This is one reason I don't think teens ought to date. This is not the age to be tied down to anyone one. There is too much growing and changing that is done.
Concentrate on school don't worry about long term dating.