Henry Clerval and Victor Frankenstein see the world in almost completely opposing ways. Henry is a Romantic, someone who responds emotionally to nature, to literature, to music, and the like. He is imaginative and fanciful and creative. He wrote poems and songs, and enjoyed feeling the intense emotions associated with adventure and drama. Victor says,
Henry Clerval was [...] a boy of singular talent and fancy [....]. He was deeply read in books of chivalry and romance. He composed heroic songs and began to write many a tale of enchantment and knightly adventure. He tried to make us act plays and to enter into masquerades
with characters drawn from fantastic or romantic tales of old. Victor, instead, enjoyed science and the process of trying to find out the reason for things rather than simply enjoying their beauty or mystery (as Henry would). He says,
"The world was to me a secret which I desired to divine. Curiosity, earnest research to learn the hidden laws of nature, gladness akin to rapture, as they were unfolded to me, are among the earliest sensations I can remember."
These are the pursuits that make him happy, the triumph of discovery after intense investigation. Thus, Henry wanted to feel deeply and appreciate things while Victor wanted to discover things he could know.