The Big Bang Theory initially focused on the friendship among four geeky scientists, Sheldon, Leonard, Howard, and Raj, and their beautiful wannabe actress neighbor Penny. But when the show added two more ladies to the mix, Bernadette and Amy, it also saw its share of romantic relationships.

Leonard and Penny dated others before (and in between) tying the knot, while Raj dated a string of women throughout the latter part of the show. And other major romances blossomed with members of the core group.

Which were the best? Here’s a ranking of every major relationship from the series, and approximately how long they lasted.

Penny and Kurt (4+ Years)

Kurt was Penny’s boyfriend from way back when. He was a strapping, muscular man who was the complete physical (and intellectual) polar opposite of Leonard. Penny lived with Kurt for four years after they moved to California from their hometown of Nebraska, though it’s unknown how long they dated prior to that.

Not the sharpest tool in the shed, Kurt was also arrogant, condescending, and a bully. He was initially Leonard’s biggest rival before Leonard finally won Penny’s heart. Penny referred to Kurt as a jerk and they broke up presumably after he cheated on her. That’s when she moved into the apartment next door.

Penny and Zack (On and Off)

An on-again, off-again boyfriend of Penny’s, they met when she worked at The Cheesecake Factory and dated on and off for quite some time, though it was never for the right reasons. At one point they accidentally got married in Las Vegas on a whim, thinking it was a joke, though they later had the marriage annulled.

A dimwitted but kind soul, Zack was not as arrogant as Kurt but not nearly as smart as Leonard. Zack really didn’t offer much to the relationship for Penny, but he was definitely perfect for her as a friend.

Raj and Anu (Under a Year)

The courtship between Raj and Anu at first seemed forced. It was more like a business transaction as they were pursuing the option of an arranged marriage since they were both ready to settle down but hadn’t yet found the right person. The relationship slowly improved as they appeared to grow to genuinely like one another.

But it quickly became evident that they were two very different people and it just wasn’t going to work out. After waiting so long to find his perfect match, had Raj opted to stick with Anu, he would simply have been settling for someone who wasn’t right for him.

Leonard and Priya (About A Year)

Priya, Raj’s younger sister, was a total mismatch for Leonard. She seemed intent on changing him and had no desire to pursue a real, long-term relationship.

She was smart, beautiful, and funny, but she often got annoyed with him, was controlling, and seemed more focused on her career as a corporate lawyer than anything else. Leonard was even willing to move to India with her, but in the end, her jealousy of Penny and insistence that he cut ties with her marked the end of their romance.

Raj and Lucy (Under a Year)

High on the social awkwardness scale, Lucy seemed almost like a female version of Raj, which made them a good match, but also made them a pairing that would never last. She tried hard to get over her social anxiety, just as Raj did — remember when he wasn’t able to speak to women?)

Their dates were sometimes awkward, but there was something endearing about them. In the end, however, Raj’s overbearing nature was too much for the shy woman to handle.

Raj and Emily (Over a Year)

Emily actually seemed like a perfect match for Raj. Beautiful and smart, she seemed really into him. She too was quirky and didn’t appear to shy away from his eccentricities.

They had a lot in common, including both having gone to Harvard and working as doctors, she as a dermatologist. But in the end, Raj blew it by cheating on her, though they also supposedly had troubles in the bedroom. Still, of all Raj’s girlfriends, Emily is the most likely candidate to have been the one.

Stuart and Denise (Still Going)

A total comic book geek, Denise was the woman Stuart had been looking for all his life, so when they crossed paths and she began working at his store, it was fate.

The two were totally cute together, equally awkward and geeky. They bonded over their mutual love of comics, Star Wars, and everything in nerd culture, and began spending every waking moment together. It was nice to see Stuart not only finally getting a date but meeting someone who was his true partner and whom he could be himself around.

Howard and Bernadette (Marriage)

Howard and Bernadette dated for some time before eventually moving in together, getting married, and having two children. While their relationship sometimes seemed odd with Howard sometimes appearing closer to Raj than he was to his wife, as well as being lazy and self-involved, it was ultimately a good match.

Howard was also super close with his mother and Bernadette often emulated much of his mother’s behaviour which can seem creepy, but also worked for them. And they had clear chemistry with one another, even if they bickered a lot.

Leonard and Penny (Marriage)

The relationship that served as the backdrop for much of the series, Leonard pined for Penny from the moment he saw her. And while he was the complete opposite of anyone she had ever dated before, they clicked in their own special way.

Penny matured a lot from when they first met, thanks to Leonard, while Leonard developed a greater sense of confidence and assertiveness thanks to Penny. In the end, they ended up together, married, and, as the series ended, with a baby on the way.

Sheldon and Amy (Marriage)

Even Sheldon’s mother thought her son was doomed to be alone for life, so when Sheldon met Amy, it was destiny. As the only person who could rival Sheldon in smarts, he respected Amy’s intellect tremendously while she worshiped him and wanting nothing more than to be with him in every way.

Their romance bloomed as Amy helped Sheldon open up and become a better person. She put up with a lot and was always patient with Sheldon and his egotistical ways and inability to properly interact with others. As partners both romantically and professionally, they ended up on top of the world.