I remember reading this novel ten or more years ago. The prologue had the narrator reminiscing of Tokyo Bay and condoms floating onto the shore. The protagonist seems to be an immortal or incredibly long-lived human with powers to create or morph planets to his liking. There appear to be numerous similar individuals of different alien races who travel around the Galaxy, creating hospitable worlds. I think one of the worlds had silicon-based life on it.
Life is a thing—if you’ll excuse a quick dab of philosophy before you know what kind of picture I’m painting—that reminds me quite a bit of the beaches around Tokyo Bay.
Now, it’s been centuries since I’ve seen that Bay and those beaches, so I could be off a bit. But I’m told that it hasn’t changed much, except for the condoms, from the way that I remember it.
I remember a terrible expanse of dirty water, brighter and perhaps cleaner way off in the distance, but smelling and slopping and chill close at hand, like Time when it wears away objects, delivers them, removes them. Tokyo Bay, on any given day, is likely to wash anything ashore. You name it, and it spits it up some time or other: a dead man, a shell that might be alabaster, rose and pumpkin bright, with a sinistral whorling, rising inevitably to the tip of a horn as innocent as the unicorn’s, a bottle with or without a note which you may or may not be able to read, a human foetus, a piece of very smooth wood with a nail hole in it—maybe a piece of the True Cross, I don’t know—and white pebbles and dark pebbles, fishes, empty dories, yards of cable, coral, seaweed, and those are pearls that were his eyes. Like that. You leave the thing alone, and after awhile it takes it away again. That’s how it operates. Oh yeah—it also used to be lousy with condoms, limp, almost transparent testimonies to the instinct to continue the species but not tonight, and sometimes they were painted with snappy designs or sayings and sometimes had a feather on the end.
Of course, the rest fits the description - long-lived hero that creates whole planets etc.