For the record here's a list of all the Japanese voice actors in the Metal Gear series who have died since voice work in the series began in 1998:
Chikao Ohtsuka (Big Boss, heart failure)
Takeshi Aono (Colonel Campbell & Granin, cerebral infarction)
Kaneto Shiozawa (Gray Fox, cerebral contusion)
Kōji Totani (MGS1 and 2's Revolver Ocelot, heart failure)
Kazuyuki Sogabe (Psycho Mantis, cancer)
Daisuke Gōri (Scott Dolph, suicide)
Kenji Utsumi (Colonel Volgin, cancer)
Kazumi Tanaka (The Fear, pulmonary heart disease)
For a series with such a relatively limited amount of characters, that's a large amount of people