What do you mean by long run? Most retail products don't appreciate over time like Lego and other limited run items.
If you mean good short term flip material then almost everything beats Lego. Difference is you have to source and sell it continually to make money whereas with Lego you just sit on it and sell much less frequently. Lego is much more passive than regular household items which means far better hourly pay. Walk into any chain store in the country and you will find lots of household items with great ranks that make 30% ROI within a month. Do some research on getting discounts to buy online and you will find 100-300% ROI within a month.
We do 10% Lego and 90% other toys and household items (home and kitchen, tools, health and personal care, beauty, grocery etc). Started with Lego but branched out 2 years ago. Like Lego start with another niche, learn the ropes, send in product, master it and then move into the next niche. For each niche you will learn the best items to buy, when the good sales are, ideas to create your own bundles, best keywords for your PPC campaigns etc. With Lego you don't have to do any of that, but the returns are far less as well because it is such low hanging fruit. Obviously the big revenue is in private label and wholesale but profit margins are much less (around 10%).
IMO Lego still gives the best hourly rate if you can store it at home and sit on it for 3-4 years. OA and RA gives good hourly rate with good consistent cash flow. Wholesale and private label gives the best cash flow but much less hourly rate after all expenses. Lots like to mix RA, wholesale and private label. Plenty of opportunities and the sky is the limit. Like anything simply takes an initial investment of time and capital and you will take your fair share of failures along the way.