I knew Heat would make the list!Heat and Blackhawk Down were pretty well done. The combat scenes in Band of Brothers, especially Brecourt Manor, were fantastic.
The Killer Elite was also really well done, based on Ranulf Fiennes book, the Feathermen.
And for an oldie, The Siege at Firebase Gloria was a good shootemup.
Unrealistic? Everything including the above. They are just the least unrealistic. I don’t think you can truly portray combat on a screen.
Oh and the village assault in a Tears of the Sun.