From communications satellites (the geosynchronous 'Clarke orbit' is named after him) to encrypted smartphones (described vividly in Imperial Earth), to space elevators (The Fountains of Paradise) - he introduced so many ideas that are now regarded as unremarkable. (I remember being attacked and ridiculed in high school when I brought up the preposterous subject of space elevators...)
His writing was more stylistic than Asimov's, and while not as prolific, his novels and scientific writing were equally inspiring. Clarke had a poetic, fantastical side, revealed in stories like 'The Lion of Comarre' and 'Against the Fall of Night'; relating visions of vast vistas of space and time (reminiscent of Olaf Stapledon), but also with a subtle discontent and yearning in the protagonists. I fear much of this subtlety is lost among modern readers, but it shouldn't be - so many of us suffer from that same malady!
Clarke and Asimov were great frenemies, and their exchanges were hilarious. They both had gigantic egos! And I just now realized a way to characterize their literary personalities: Asimov resided in temperate New York City, while Clarke had his home in tropical Sri Lanka. But the historic names of that place - Ceylon, Serendip and Taprobane - were even more exotic and evocative, just like the best of Clarke.