Let's see...
Baldur's Gate series: Allows for a lot of flexibility in character creating, tactics, proper inventory, so many companions with interesting personalities (though in BG1 they have little to no content), great and engaging stories and awesome villains along with some fun and quirky dialogue choices. Also, mods. So many mods.
Mass Effect 2: I loved all the different crew you could get, I found them all interesting to get to know. The story was pretty entertaining too up until the end boss. As with ME1 we get the dreaded dialogue wheel which kills the range of conversation choices.
KOTOR 1: Fairly entertaining characters and plot, with that one major plot twist of course. Great to delve into the Star Wars universe and create your own character in it. The back and forth between characters could be quite fun.
NWN: Hordes of the Underdark: The first chapter can get a bit tedious on replays, but the other chapters although a bit simple in terms of plot are pretty good. The new companions were great too.
DA: O: Awakening: Interesting companions! Sadly still very buggy to this day unless you use mod fixes, but I liked it overall.
NWN: Shadows of Undrentide: I've only played through this one a couple of times, and it is pretty good. Especially when you pair it with HotU, gives your character a nice story across the two. Suffering from a little of the NWN blandness though.
DA: Origins: I only found a few of the companions actually interesting, and overall found it a bit dull (liked Awakening much better). Still, story was decent and the it was a good introduction to the world.
SW:The Old Republic: Despite being an MMO they manage to give you a nice variety of stories and companions, what is perhaps most impressive is that each class has their own different story. Every conversation and quest is done as a cinematic so you can see the characters as you're talking to them (looking at you DAI). All round it is pretty entertaining and a great way to learn more about the universe. The downside is on your replays even if you pick a different class you're just redoing all the non-class quests again unless you switch sides. And of course the nickel and dime you for every little thing if you're not a subscriber, and even if you are.
ME 1: I found... quite dull. The companions especially, just... flat. When I look at those same companions in ME2 they've been given more personality and life, but looking only at their ME1 versions I wasn't left terribly impressed. Probably didn't help that I disliked the first-person shooter aspect of it either. Story is fairly run-of-the-mill sci-fi. I found a lot reminding me of Star Control 2.
DA 2: Well the characters weren't boring, even if they were quite idiotic at times. The jumping about and magically appearing enemies was silly and the area reuse was blatant (area reuse has been in past games a lot as well, but it was very obvious in this) Story was very fixed, but ehh, it wasn't too bad. Much to my dismay it got infected with the ME dialogue-wheel and god-awful inaccurate paraphrasing. Oh yeah, race choices? What race choices.
NWN: Original Campaign: Bland. Boring. I think it had potential, it should have been good but agh it's just terribly mind-numbing to even play.
DA: Inquisition: Pretty interesting and diverse characters, story seems like it's building up to be good... but then it just appears to stop abruptly. I felt like I was halfway through the plot when I started heading towards all the end game stuff. Admittedly I got sick of all the MMO grinding quests and just skipped all non-story or companion quests after a certain point (and I'm someone who loved exploring every single map in BG. In DAI it just gets tedious) Still, it feels like half a game. All the fetch quests may have been a bit more engaging if they'd had proper cinematics for each conversation, but half of them are also just finding letters all over the ground. Unfortunately DAI has also been infected with the autodialogue of ME3 as well as the dialogue wheel and paraphrasing that its predecessor picked up from ME. Ugh.
ME 3: Story-wise ME3 is pretty decent. Characters aren't really bad either. The reason I rank it so low is because it tosses out so many RPG and choice elements. I thought the dialogue wheel and paraphrasing that accompanied it in previous ME games was bad, the auto-dialogue is worse. Your character does so many things that you have absolutely no control over. They screwed over the ME2 characters (seems like they wished ME2 hadn't existed) and I'm not even going to get into the ending. It's such a shame because it could have been so much better.
And Jade Empire I still haven't played yet.