What are the best performing exchange-traded funds (ETFs) available to investors in Bulgaria that offer strong long-term returns, portfolio diversification, and exposure to Bulgarian, European, and global financial markets? Which ETFs focused on sectors such as equities, technology, emerging markets, energy, dividends, and fixed income have delivered the highest historical performance based on returns, liquidity, and asset growth? How do Bulgarian market ETFs such as the SOFIX-based funds compare with international UCITS ETFs in terms of risk, expense ratios, diversification benefits, and long-term investment potential for Bulgarian investors? Which ETFs are considered the most attractive investment options in Bulgaria based on historical performance, market stability, investor demand, and portfolio growth opportunities?