The MSX games were good, and ahead of their time at release. However I think MGS on the PSX is the first one that truly captured the sense of sneaking about.
However you can play both of the original MSX Metal Gear Games on the PS2 as they are included in the Metal Gear Solid 3 - Subsistence release. Which is actually the first time Metal Gear 2 actually had an official English translation version released. Before this you could only get a fan translated version.