The hadith you are talking about was narrated in both Bukhari and Muslim as follows:
لايؤمن أحدكم حتى يحب لأخيه ما يحب لنفسه
None of you [truly] believes until he loves for his brother what he loves for himself.
It doesn't mean that you will become a disbeliever if you don't love for your brother what you love for yourself, rather it means that your Imaan is not going to be complete if you don't have that quality.
Another narration of this Hadith in Musnad Al-Imam Ahmed:
لا يبلغ العبد حقيقة الإيمان حتى يحب للناس ما يحب لنفسه
The servant does not reach the reality of [or true] faith until he loves for the people what he loves for himself
For more information, check out this [link][1]link
Allah knows best! [1]: http://en.islamway.net/article/13371/an-nawawis-forty-hadeeth-no-13