I'm talking about top-down/isometric CRPGs like Baldurs Gate. It's a genre that I really want to get into but I'm struggling a bit.

I tried out Baldurs Gate but found it far too difficult. The classic D&D style mechanics seemed to go largely unexplained and everything post-tutorial seems to murder me!

Are there any of these games that have a more forgiving learning curve or something that would help me understand D&D mechanics a little better?

You could try Fallout. If you build your character properly, it's pretty easy, and it's loads of fun. If you care about how to build your character, PM me and I'll tell you - it's a fairly overpowered, yet roleplayable build, but that's the point for the first playtrough, Fallout can be quite unforgiving.

Actually Baldur's gate is (IMO) hardest at the start, and if you persevere you'll find it will get easier. The problem at the start is that because even your fighters have so few HP, an unlucky roll of the dice will wipe someone out. Once you get slightly more defined characters then it becomes very obvious that you send in your high HP chars into the fight while your wizard, and thief hang back with the ranged weapons.

Baldur's Gate is quite punishing early on, due to your low starting HP, though if you stick with it, you'll probably do a lot better after a while. Check some character optimization guides online (there are plenty), if you don't know where to put your skillpoints.

Dragon Age: Origins is relatively similar to Baldur's Gate (different rule system but the basics are similar), and it does a better job at introducing the mechanics than the old D&D games did.

The Geneforge games are fairly simple to understand, as long as you have the tolerance for the lo-fi graphics.

Planescape isn't really a good representative of CRPG genre since it's fairly unique, and Neverwinter falls quite short in campaign experience (unless you use user modules, obviously)

The original Neverwinter Nights campaign does indeed suck, but I've heard that the expansions are a lot better, and of course there's all the fan made stuff.

Torment I'd say is a good game to familiarize players with the Baldur's Gate and Icewind Dale rules, apart from that, sure, it's an unusual CRPG.

Planescape Torment is what I would recommend too.

Here is a beginners guide, that you may find helpful.

http://www.gamefaqs.com/pc/187975-planescape-torment/faqs/48406

Think I'm gonna give Planescape Torment a try, and I'll look into the other suggestions as well. Thanks for the suggestions everyone :3

From what I've gathered Planescape has easier combat but more focus on the story? I think it sounds interesting. At the very least it should familiarize me with the genre a bit.

Baldur's Gate is probably hard because of it's RTwP nature too. Admittedly I found it easy to get into at that time, but YMMV.

Perhaps you'll want to try Dark Sun: Shattered Lands. It uses AD&D 2e if I'm not wrong, but it's easy to grasp, and the graphics hold up very well even by today's standards (if you compare it with lower-budget games).

Planescape is definitely easier than Baldur's Gate to play, so I recommend that too.

Planescape is one of the best games of all time. But I would not really recommend it to first timers for two simple reasons:
Text walls!
And the fact that you will be able to appreciate just how different it is once you have some genre experience under your belt. They are better, but still bad. User made content is the only way to go.

It is the best story-based RPG you will ever see, but it will not familiarize you with the genre at all. It's an interactive book basically, and all combat or character development as far as experience gain goes is pushed to minimum (or just pure annoyance.) It's one of my most favourite games ever, so I'm not trying to turn you off for no reason - I'm saying it because I know what I'm talking about. PST is completely unique. Games like Arcanum or Fallout will do a much better job of introducing you to the genre.

I really wouldn't recommend PS:T as a game that would solve your concerns regarding the genre. Yeah, it has a fantastic story and yeah it is easier, but the D&D does still go entirely unexplained.
The Fallouts are what you're looking for. The SPECIAL system is way, way easier to pick up.

In case you ever get the itch to play them or if GOG ever manages to get them here, the old AD&D Gold Box series, they up till Treasures of the Savage Frontier and Gateway to the Savage Frontier used a version of 1st edition rules and can be quite umm..challenging especially Pool of Raidance which much like Baldur's gate starts you off at level 1, there pretty good with a nice(in my opinon) turn based tactical combat system that resembles moving minitures around a battle field ala a table-top game where you really have to plan your turns well. The only thing that maybe a turn off is the veiw window in town/dungeon mode is a bit small and to save on memory and space they put alot of text in printed journals which the game(s) would every so often would tell you to read a passage from the journal.