A bit more in-depth info:
Top Hunter and Spin Master are side-scrolling platformers reminiscent of Gunstar Heroes, Joe and Mac, or any similar run and shoot game. Top Hunter is fairly challenging and requires approximately two hoursto play through. Spinmaster is a very easy game and can be completed in less than an hour.
Nightmare in the Dark is a very easy puzzle action game in the tradition of Bubble Bobble and Snow Brothers. It can be completed in under half an hour and is very repetitive in its patterns. It features a wonderful soundtrack and superb Halloween-type backgrounds.
Spinmaster is the most solid of the games due to impeccable control and fast-paced action. At the going rate of under $100, it will provide lots of fun. Top Hunter will provide more replay value as there are a few hidden areas and the levels can be selected in different orders. Good deal for under $100 as well. NitD is a conversion cartridge and will be more expensive as such. Probably not worth it unless you hear the music beforehand. One of the best soundtracks on the Neo, along with Pulstar, Shocktroopers and the Metal Slug series.
Sincerely,
Mikhail