T2 has had 3 releases...the Live one, the Extreme, and Ultimate. I have the original snap case Live one and the Metal Ultimate.
Spiderman new 3 disc one is the same as the original except for the 3rd extras disc. The Superbit Spiderman is just the film but with commentary from Tobey. If you have the original release, I'd go for the Superbit.
Robocop: Criterion and MGM new release Trilogy...The new Trilogy RC is the director's cut but with a better transfer and Dolby 5.1. Same commentaries. New release is worth it, plus you get 2 & 3 as bonuses.
Some people do enjoy special editions over regular releases...it just depends on what extras or enhanced features are present over older or standard ones.
The Final Countdown special DVD had a bonus disc featuring interviews with the Jolly Rogers.
It all depends on you...what do you want...bare bones release...extras up the wazoo...do you love the film?
Underworld: The double dipped one has more extras...if you really lik ethe film, I guess I'd get it over the standard...the prices are very identical...if you liked the film.