Take the time to say it.
“You know what I really like about you…”
“I love it when you…”
“I really respect you for…”
“This thing you did had such a good effect on me…”
“Thank you for…”
“I really appreciate it when you…”
“I admire you for…”
“One of my favorite memories of you is…”
Accentuate the positive in others and you may just have as positive effect on someone else as they have on you.