Yeah, I'll be the first to admit Soulblazer is a bit weak at the beginning. Grass Valley is pretty bland, and some of the first dungeons really don't stand out as anything special. Fortunately, the game gets a little better once you reach Greenwood, and really, really picks up once you reach the third world, St. Ellis Sea Bed.

Illusion of Gaia is much more player friendly than Soulblazer. I'd say the biggest advantages it has over Soulblazer are its more refined story and combat system. Soulblazer has much better exploration elements, and a better stat system as well as spells and equips, but Illusion has much more freedom in battle. The characters are also much more fleshed out in Illusion.

Overall, I'd rate the two games about the same. It's really just a matter of preference. If you didn't like Soulblazer, then by all means jump right in to Illusion. You won't be missing anything storyline wise aside from one boss cameo.