As the magazine says in the article:

In selecting this year’s winners, Global Finance’s editorial team considered objective and subjective factors. Objective criteria included growth in assets, profitability, geographic reach, strategic relationships, new business development and product innovation. Subjective criteria included the opinions of equity and credit-rating analysts, banking consultants and others in the industry, as well as corporate financial executives. The winners are not always the biggest banks but, rather, the best banks – those with the qualities that corporations should look for when choosing a ban

You can read the article and the winners  here.