Hello Yishai!
A score or MIDI file normally doesn't sound good by itself, just because you use good samples. The playback has to be fine-tuned (articulattions, dynamics, note lengths, starting positions, mix, ...).
As a first step you might want to try the Finale Human Playback Preferences for the Special Edition we provide. These settings take care of automatic articulation changes according to your notation marks.
http://www.vsl.co.at/en/MyDownloads/Notation_Related
Best regards,
Andi
Vienna Symphonic Library