Silken tofu definitely helps, and a bit of honey (*gasp!*) or agave to sweeten. Bananas make smoothies thicker, smoother and SWEETER. If you're using something else, you have to replace that mild, creamy-sweet effect that bananas have.
It's fine, my kids and I don't like bananas either. We always use frozen fruit (rather than fresh), a little sweetner and a 1/2 package of silken tofu. No bananas needed.
If you think your smoothies are "missing something" without bananas though, it's possible you actually LIKE them in smoothies and just don't like them plain.