作为“我想你”,可以是一直在想,或是过去想,或是以后会想,所以以下的都会用到：
I miss you.I've been missing you all this time.I've always missed you.I missed you.I'll always miss you.
可是作为“我错过了你”（没碰上你）,一般都是已经发生的事情,所以常见的是过去时,但也可以是将来时,现在时就很少见：
I missed you that time,but I'll make sure I won't miss you again.