This is a hard one. First and foremost I dont believe there is any thing like 'best forex broker'. Ideally, what one should look for in a forex broker is how well the broker suit his needs, for instance a scalper would prefer a broker with very little spreads, a trader who trades during times of high volatility or who generally leaves a trade open for say a week, month etc will prefer a broker that guarantees stops. Other peculiarities of a broker can be observed when one trades with more than one broker e.g. a broker who is more prone to stop hunting.
Of great importance when choosing a broker is that the broker must be regulated. CFTC and NFA for an American company and FSA for a UK Company (Many Kenyans are likeable to .uk firms)
That said here goes my list
1. ACM (A Switzerland company, I hear that they guarantee stops. But are stringent on ua country of resident, they called me and told me that I cant open an a/c with them since I reside in Kenya)
2. FXCM (They are highly competitive, offer wide range of tradeables including stock indeces, They are listed in the NYSE)
3. Forex.com (My live account is with them, so far so good)
(Note: The above list is biased coz I dont have enough experience with other firms)
Others
4.Oanda (Ranked the best in the world according to polls)
5. GFT Financial
6.Fxpro(Sponsors some premierleague teams, but I understand have issues with paying u ur moey: Why trade when u dont get paid?)
7. Etc..... Add to and ammend the list as appropriate.
“small step for man”