I saw this too in store and thought it was too predictable a pattern to work well, but definitely too weak to see since they weren't that easy to see in the shadowed box it came in. I still don't understand why that couldn't randomize it better. As advanced as programming circuits have gotten, it should be pretty easy and cheap to manufacture.
The best thing I'd say that would work for a true random thunder/lightning effect would be getting a super bright light hooked up to a color organ. Gemmy used to sell super cheap plug and play ones - called Lightning FX for the Halloween versions which were black with an orange thunderbolt, and titled something like "Christmas FX for the x-mas ones which were green/white with a red x-mas tree - if you find one for under $50, it's a bargain now. Run that with a thunder sound track and you'd have a perfect storm effect. I have no idea why they discontinued making these and now all you can find are the horrible expensive substitutes.
LOVE the Clue movie poster in the background. If you haven't seen it, check out "Murder By Death" (1976) for a hilarious all-star cast, credit illustrations by Charles Addams (cartoonist/illustrator that created "The Addams Family") and overall great script by Neil Simon. (this is my favorite movie of all time)