If you want to see some of the earliest examples of Amiga software, take a browse through the first 50 or so disks in the Fred Fish series. I'm sure I recall seeing files with 1984 and 1985 datestamps on some of his early disks. While he may not have started his collection before the Amiga was widely available, I seem to remember his disks were a mixture of new, current and old.
(Disk 5, for example, has programs dated January 1985)
I must confess that, back in the day, I would rather have slashed my wrists than explore any of these "Fish Disks". To me, they were the single most boring thing you could do with your Amiga - the electronic equivalent of watching paint dry; fossilised remains of zero interest to an eager upstart, constantly on the lookout for flashy, shiny things.
With the benefit of hindsight, there's probably a wealth of undiscovered Amiga artefacts contained on those early Fish disks. Or perhaps not. Maybe they're as uninteresting today as they ever were!
As for commercial software, and going off-topic, I think it's widely agreed that Mindwalker was the first "leisure" retail release for the Amiga, in the USA. The UK's first leisure/entertainment retail release was probably either Brattacas by Psygnosis or Lands of Havoc by Microdeal. As for application/utility release... Graphicraft/Textcraft/Musicraft? Doesn't Andy Warhol use Graphicraft at the A1000 launch? It'd be interesting to research some sort of timeline..