Big games vs medium ones

I have a big list of games to catch up with so i choose games for less than 30-40 hours long. Now, i want to start with a big one such as skyrim, RDR2, witcher 3 and then soul games. Been reading online and found out that people have 300+ hours on those, in my calculations 2 hours playtime daily means 150 days and i am a slow player i take my time. Skyrim is my first choice for now, does it worth to spend almost 6 months on a game. Meantime, i can finish 15 medium long games and strike it off my list. P.S does Skyrim has an end, with the side quest? Read that people still playing for years. (Not interested in mods) just main campaign and all sides.