Love between a man and woman? Parent and child? Child and pet? Gardener and his garden? Artist and her art? Think beyond the term 'love' and you'll figure it out. Remember that 'love' is a feeling that comes and goes and it is not a state of being.
Conflict! Love Triangles, obstacles, doubts about the Partner, doubts about yourself, discovering (major) flaws in your partner but still loving them? Or mix in a 2nd genre that creates tension naturally like a thriller or a mystery
I think for it to be really good, it must contribute to character growth in some way. Overcoming issue with commitment/trust/intimacy are good. Developing a strong FRIENDSHIP in addition to love is a must. The characters must be comfortable together clothed. I stopped reading romance in HS because I got tired of one dimensional characters whose only goal was to take each others clothes off. But, one dimensional characters are a problem for any genre.
For the same reasons you named, Romance is one of my least favourite genres. Characters are so often reduced to their looks and many of the often used stereotypes (love at first sight, god-like flawless man falling for uninteresting average woman) are plain ridiculus.
The "will-they-wont-they" drive can be extremely powerful. If there is chemistry between two people, but something keeps them apart (whether it be external obstacles or internal insecurities) it can really draw readers or viewers into the emotion of it. They want these two to get together, they're rooting for it, waiting for it, almost screaming at you as the writer to do it. Then when they finally do, it is immensely satisfying. I think TV-Tropes calls this one "Unresolved Sexual Tension." It's a good one.
I think a great love story is characterized by the couple overcoming something together. They might triumph over their own shortcomings, enemies, sickness, etc. Love that is tested and refined by sacrifice and hardship is so much more meaningful.
There has to be a powerful reason for the couple to be together (love, chemistry, etc.) balanced by an almost-as-powerful reason for them to be apart. That's what creates the tension and drama in a good romance. It's hard to write good contemporary romances because there really aren't that many reasons for two people who are in love to not be together, without resorting to melodramatic and unlikely scenarios. With that in mind, I agree with @KhalieLa that often the best reasons for characters to be kept apart are internal - for whatever reason, one or both of them has a psychological barrier to being in love with the other.
Ironically, the love story that has stayed with me the most in the books I've read in recent years was the one between Emma and Dexter in One Day. I guess something about the unhappy, bittersweet ending makes it so much more powerful than the happily ever after. I think that is something to consider if one wants to write a love story that stays with the reader forever after.
Yeah, there's definitely a distinction to be made between a Love Story and a genre Romance. Romeo and Juliet is a successful love story, but it doesn't fit the Romance genre at all.
