The key is to not come to him with the premise that he doesn't please you. You can find positions and ways to reinvent your sex life. Find resources that help you or investigate options. Then bring them to your husband. The best way to bring this up is to investigate how to communicate about sex. My favorite is Mars and Venus in the Bedroom although there are others. Use this information to come to him and say something like "I wanted to try some new things in the bedroom; what do you think" and let him pick up the ball running. Create a scenario where you are helping you as a couple be better and more adventurous lovers.
The position or method isn't as important as getting him to try new things. He will be open if you bring it to him in a way that suggests that you aren't saying he is inferior. If he feels inferior that will effect his ego. If you learn to discuss it as a couple who want to try new things then it is a project worked on as a couple. If you tell him he doesn't satisfy you then that tells him he is a subaverage lover.
Resources such as the Joy of Sex can benefit both of you. He may be flattered that you want to have a great sex life. It is very gender specific for a guy to want a partner who cares about the sex life. That is the approach you want to take
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