Possibility of offer retraction

I received a job offer and they gave me 2 weeks to make a decision. Its a great company that is up on list of places I like but Im currently talking to another company that I like.

Is there a possibility that the first company will retract the offer in those two weeks? What if they find a candidate that is better than me in those two weeks? The first company interviews a high number of people and is well known so I doubt they lack qualified candidates or can find a better one in those those two weeks.

Should I just accept right away?