There are many, many high-quality plug-ins, soft synths, and sample libraries. Of the various free and not-free soft synths that I have, the best are probably Arturia's V Collection:
https://www.arturia.com/products/analog-classics/v-collection/overview
However, my opinion is no doubt influenced by the fact that the V Collection includes a digital recreation of a Moog Modular synth, which I've wanted ever since I was in junior high school way back in the early 1970s.
https://www.arturia.com/products/analog-classics/modular-v/overview
Most commercial DAWs come with a set of their own virtual instruments, although the number of instruments varies depending on the particular edition of the DAW, since the number of instruments and effects included with the DAW tends to be the determining factor as to how expensive the DAW is. But some DAWs take a different approach-- they don't include a lot of instruments and effects, such that the cost of the DAW is minimal, and then you can buy and use whichever third-party plug-ins you want. Other DAWs limit you to the types of plug-ins you can use with them (e.g., VST plug-ins, or AU plug-ins, or whatever).
Note that I'm just a dabbler with a very limited budget, and my interests lean more towards electronic music, so I don't have experience with some of the high-priced orchestral software, but some of the ones I've heard of are Garritan, EastWest, IK Multimedia, and UVI, to name a few:
Garritan Virtual Instruments & Sound Libraries
EastWest/Quantum Leap - Award Winning Virtual Instruments
IK Multimedia | Miroslav Philharmonik 2
http://www.uvi.net/en/orchestral-composer/orchestral-suite.html