Even though it's obviously a completely shallow copy of the original, it's still a fun watch for the following reasons:

• All of Egon's lines.
• All of Venkman's lines.
• Peter MacNicol's character.
• The whole "World of the Psychic" scene
• The whole courtroom scene (as you mentioned).
• The overall concept of the haunted painting is pretty fun, but I think in combination with the mood slime idea it overcomplicates things. However, there are some fun moments with the slime.
• Louis and Jeanine's romance has some funny dialogue, though that storyline kind of wastes time that could've been spent on more fun supernatural stuff.