If you don't mind a steep learning curve, Eastwest Hollywood Orchestra can't be beat in terms of value for the money right now:
Hollywood Orchestra
For 450$ you get all the instruments of the orchestra, tons of articulations, and all recorded to professional standards. It cost several thousand dollars some years ago, and it still costs you several thousands were you to buy a comparable amount of samples from any of the competitors. If you don't like Eastwest, Vienna Symphonic Libraries Special Edition and Special Edition+ is a great option. But you need a reverb for it, and know how to handle it. Not as complete a set as the Hollywood Orchestra, but you can get a lot of mileage out of it.
If you want to do trailer and don't need individual instruments, have a look at Spitfire Albion and Metropolis Ark. These offer instrument sections only, mind you. So if you want to write a line for a single oboe, you can't do that with these libraries. You'll have flutes, oboes, and clarinets stacked together. This might be a help (for working fast, or if you know little about orchestration) or an impediment (little control over orchestration).
If you are looking for a vintage hollywood sound, Cinematic Studio Strings are a great option. They are easy to work with and you'll learn to use it quickly. What they do they do exceedingly well. But due to it's specific sound it isn't the best option for all-purpose strings.
Another very good string library that can be bought for a very reasonable price are Light & Sound Chamber Strings. Very versatile sound. Smaller section sizes, but its probably good for everything except huge trailerish braaaaaaaam. Maybe a bit harder to learn than Cinematic Studio Strings, but right now you'd get a complete string library for 150$ or so (they are on offer right now. Click on the buy button to see the price - oddly the offer isn't advertised on their homepage).