The Agarest War games do it pretty well, although it's not perfect. Some relationship points come from "pick who you want to help out" which will obviously improve the relationship with that girl, but a lot of it comes from dialogue choices either while talking to them (meaning saying the wrong thing could lower the points) or, my favourite part, things that have nothing to do with them. Things like "pick which strategy to adopt" will affect your relationship with the ladies. Like one might like it more if you make a more aggressive choice (like charge the enemy front lines) and some may like it better if you take a more conservative approach (like avoid battle if you can).

Because of that it makes it much less obvious who you're going to end up with if you're not using a guide and I like to see who I end up being more compatible with just based on the choices I would actually make if I were in that situation. It's still not a perfect system, but I do like it.