Speaking of MGSV, i've not yet finished that game. It's funny. I've completed almost all of the entire series not counting the acid titles since I've never played them. Not fond of card games like that. The three games I cannot seem to complete are MG Portable Ops, MGS Peacewalker, and MGSV. I not sure why that is. Maybe I find that they go on for too long where-as the earlier games were the right amount of playtime and the only thing I had to focus on was the mission at hand--not constructing and running a business.
Peace Walker is the REAL Metal Gear Solid V.
Hideo Kojima even confirmed as much in several interviews during the game's development -- the development team actually referred to it as Metal Gear Solid 5 during production. The general inference seems to be that Konami wanted Metal Gear Solid 5 to be a big AAA console release instead of a handheld game, and made them change the name prior to release to reflect this.
And trust me, the finale of the game is SO WORTH THE EFFORT. Finish it.
The HD remaster is pretty definitive, and the Metal Gear Solid 4 style controls make it a bit easier, if that helps any.
As for the Ac!d games, I love them. 2 was definitely better, but one can appreciate that they have their own independent canon that branches off from Metal Gear 2 and assumes MGS never happened (so as not to screw up the official timeline). It also was a pretty novel reinterpretation of the MGS playstyle, and it bums me majorly that they were never released on the PSN.
Portable Ops was... okay. It didn't tell us anything we didn't already know if we'd played Snake Eater and listened to what Liquid and Big Boss had said in prior entries, but it was a commendable attempt at bringing the playstyle and graphics of Subsistence to a portable format. It was mostly successful, but the issues that ARE there are pretty effing glaring. I think if it were available to download to Vita, the second analog stick would alleviate many control issues in the game, but alas, it is not. As a result, Portable Ops is best remembered as an interesting experiment that ALMOST worked, but mostly served as a testbed for Peace Walker to come along later and refine.