If you have good employees, who have worked diligently to achieve a level of success, there are several ways to give back and keep your employees happy. This will have effects on their level of willingness to work, keep them motivated and encourage them to do more.

Be transparent: above raise and bonuses, running a transparent business helps keep staff motivated. Engage in dialogues and give workers a sense of belonging. Be truthful in discussing the organizations situations and condition. Learn to run a lie free organization. This encourages transparency in workers and encourages truthfulness also.

Balanced work life: it is necessary to provide a good work environment for your employees. Give them an opportunity to feel connected to the organization so they can have an enriching work life.

Communication medium: putting in place a forum or opportunity where workers can relate and communicate ideas can help in providing organisation solutions. This can also help improve interpersonal relationships and encourage teamwork.
Recognition and Rewards: recognitions of achievements is a strong motivator, when a worker takes risk or achieved a success, it is encouraging to give rewards, bonuses, a day off etc are ways of rewarding workers

Career development: encouraging career development is a good way to keep employees happy, giving opportunities for trainings, career mentoring, personal developments are ways of making employees happy and comfortable.
Other benefits: making employees happy goes beyond the basic salary, other benefits that comes with the job could also encourage workers and keep them motivated for work. Benefits like free transportation, internet access etc are ways of keeping customers motivated to work.

Make employees part of the bigger picture: it makes sense to give workers the opportunity to make a difference with their work. A sense of direction and frequent communication gives workers a sense of belonging and makes them happier to participate in the worker process.
Keeping in touch: outside work gatherings can also help to keep workers happy. Dinner events, lunch gathering after office hours are means of strengthening bonds between workers.