The first Blood Omen is great...although you might find it a bit dated. Also, not really like the rest - it's probably closest to SR1, in that it has different abilities and items you get and an open world and some times you'd need the new abilities to progress in some direction, but it had more open world than SR1. But I think it's one damn fine game, the abilities and items were quite cool, and the story was fine, too. However, as you've played the rest, you won't get much out of the story - you'll probably just get to experience some of the stuff first hand and you'll get to see glimpses of what you haven't seen before (Elzevir the Dollmaker is one of my favourite pieces from there) but it's not really that relevant. You could safely skip it, or maybe read a plot synopsis if really interested (like this one [http://www.gamefaqs.com/ps2/914777-legacy-of-kain-defiance/faqs/25247]) but can't bring yourself to play the game.
As for BO2...it's a mixed bag. It's considered the lowest point in the series but it does have its moments. Also its downsides. The combat is better than the combat in the other games (which is pretty much non existent - just button mashing) but I'd hesitate calling it "good" or even "satisfying" - it's just so BORING. It's good at first - you can attack, dodge, block and you have to do these to kill opponents. Still, after, like, two fights you'll pick up the pattern of combat - block until the enemy stops attacking, attack until the enemy starts blocking, repeat. Over. And. Over. Again. For the whole fucking game. It's tedious, boring, and frustrating - blocks are basically godmode - you can't do anything if an enemy blocks, nor can they do anything to you. You can spice it up with some grabs and weapons - basically you can get weapons and use them in a fight, you can also grab people and 1. throw them or 2. do a light attack (usually you can make several of these before you let the person go) 3. do a heavy attack (more damage but you drop them immediately) but still the majority of what you'll be doing is blocking then attacking then blocking. To make matters worse, weapons break (if you block with them or attack a person who's blocking) but only when you use them - enemies have no problems wailing on you for days and the edge of that sword won't even dull or chip.
So I don't think it's worth getting for the fights, not really. But the boss battles were quite good, though - similar to SR1's boss battles you have to use Kain's abilities and the environment to defeat the boss, not just hit them many times. The stealth kills were also quite good - if you sneak up behind an enemy in Mist form, (so...sneaking), you get to instakill them and the methods are satisfyingly brutal and gory, furthermore, you get different kills with different weapons - and each has two different kill animations (albeit later weapons start reusing the sneak kills from the first one - like a dagger and a short sword would do exactly the same but whatever). The puzzles in the game...weren't that interesting from what I recall. Mostly "pull a lever" or "makes somebody pull a lever" after you get the mind control ability. Let's see, what else - the music wasn't bad, either. Story...eh, don't expect what Soul Reaver offered. Like at all. The Hylden are portrayed as cartoon villains and if they had moustaches, I'm sure they'll be twirling them, a lot of other NPCs seem to be lobotomised[footnote]very minor spoiler - you go somewhere and some floating seemingly magical being which is a guardian says "You must leave" then teleports you fucking nowhere near outside or anything just in a different location in the same place. You will find watchtowers with searchlights that don't do anything if you step into the light. Or how about that mansion/palace or whatever it was that Kain has to gain access to and is supposed to be heavily guarded and nearly impossible to penetrate and inside you find so many random thieves, it's like they had an infestation.[/footnote]. Then again, credit where it's due - the Glyph powered stuff was really neat, IMO. It's like steampunk but...not exactly steampunk, Glyph seems to be something halfway between electricity and just magic that is used to power all kinds of gadgets.
Overall, as I said, the game is a mixed bag. You can safely skip it and read the plot or not. Or you can even play it. I think BO1 is better, however, 1. it's older 2. you'd already know a lot of the story.
