合格 usually deals with paper materials. For example, a test or an examination. Perhaps there's also a one-time thing when it comes to 合格。 成功 deals with many aspects including life, finance, relationships, but I guess the image of success in life and in business is rather strong. Also, this doesn't necessarily happen once, but is a lifelong or a long process. I'm sure there are other interpretations but this is the fundamental difference.