One of the most common romantic Spanish sayings, which comes from the film Toy Story, is Te quiero hasta el infinito y más allá. Its literal meaning is ‘I love you to infinity and beyond’.
Some of the most used Spanish phrases, not only in the context of couples but also between friends is Te quiero un huevo.
However, you can also use the expression Eres el hombre de mi vida, if you are speaking to a man; and Eres la mujer de mi vida, if you are referring to a woman to say the same, but in a more poetic manner.